Source: http://www.google.com/patents/US5255281?dq=5,778,372
Timestamp: 2016-06-30 20:55:20
Document Index: 578156075

Matched Legal Cases: ['art.\n3', 'art 49', 'Application No. 55', 'art 928', 'art 929', 'Application No. 64', 'art 902', 'art 902', 'art 902', 'art 902', 'art 902', 'Application No. 64', 'Application No. 64', 'Application No. 55', 'Application No. 64', 'art 91', 'art 91', 'art 91', 'art 91', 'art 91', 'art 101', 'art 101']

Patent US5255281 - Semiconductor laser having double heterostructure - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA semiconductor laser includes a substrate having a (100) face as its main surface, where the substrate has a stripe of a first mesa extending in a <110> direction of the substrate and including a (111)B face as its sloping surface, a buried layer formed on the substrate excluding a top surface of the...http://www.google.com/patents/US5255281?utm_source=gb-gplus-sharePatent US5255281 - Semiconductor laser having double heterostructureAdvanced Patent SearchPublication numberUS5255281 APublication typeGrantApplication numberUS 07/996,802Publication dateOct 19, 1993Filing dateDec 24, 1992Priority dateApr 26, 1990Fee statusLapsedPublication number07996802, 996802, US 5255281 A, US 5255281A, US-A-5255281, US5255281 A, US5255281AInventorsMami Sugano, Akira Furuya, Toshiyuki Tanahashi, Makoto Kondo, Chikashi AnayamaOriginal AssigneeFujitsu LimitedExport CitationBiBTeX, EndNote, RefManPatent Citations (20), Non-Patent Citations (2), Referenced by (10), Classifications (34), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetSemiconductor laser having double heterostructure
US 5255281 AAbstract
1. A semiconductor laser comprising:a substrate having a (100) face as its main surface, said substrate having a stripe of a first mesa extending in a <110> direction of the substrate and including a (111)B face as its sloping surface; a buried layer formed on said substrate excluding a top surface of the stripe of the first mesa so that the (111)B face of the stripe of the first mesa is covered a sloping surface part of said buried layer, said top surface of the stripe of the first mesa being the (100) face of said substrate and forming a stripe of a second mesa together with the sloping surface of said buried layer, said stripe of the second mesa having a smaller inclination than said stripe of the first mesa; and a double heterostructure made up of a plurality of semiconductor layers and formed on the stripe of the second mesa, said double heterostructure having a substantially trapezoidal cross section which is determined by said stripe of the second mesa. 2. The semiconductor laser as claimed in claim 1, wherein said buried layer forms a current confinement part.
3. The semiconductor laser as claimed in claim 1, wherein said buried layer is made of a material selected from a group consisting of a semiconductor of a conductor type opposite to that of a semiconductor forming said substrate and a semiconductor having a high resistance compared to that of said substrate.
4. The semiconductor laser as claimed in claim 1, wherein said substrate is made of a p-type semiconductor.
5. The semiconductor laser as claimed in claim 1, wherein said substrate is made of GaAs, and said double heterostructure includes a first cladding layer, an active layer formed on the first cladding layer and a second cladding layer formed on the active layer, said active layer being made of one of InGaP and AlGaInP, said first and second cladding layers being both made of one of AlGaInP and AlInP but of mutually opposite conductor types, said first and second cladding layers having an energy band gap greater than that of said active layer.
6. The semiconductor laser as claimed in claim 5, wherein said substrate is made of p-type GaAs, and said semiconductor laser further comprises a first p-type buffer layer interposed between said p-type GaAs substrate and said first cladding layer, said first p-type buffer layer being made of a material selected from a group consisting of InGaP, AlGaInP and AlGaAs and having an intermediate energy band gap which falls between energy band gaps of said first cladding layer and said substrate.
7. The semiconductor laser as claimed in claim 6, which further comprises a second p-type buffer layer which is interposed between said p-type GaAs substrate and said first p-type buffer layer, said second p-type buffer layer being made of GaAs.
8. The semiconductor laser as claimed in claim 5, wherein said second cladding layer is made of n-type AlGaInP and includes a mole fraction of Al which is smaller than that of said first cladding layer.
9. The semiconductor laser as claimed in claim 5, which further comprises a p-type buffer layer which is formed only on the (100) face which is the top surface of the stripe of the first mesa, said p-type buffer layer being made of a material selected from a group consisting of InGaP, AlGaInP and AlGaAs.
10. The semiconductor laser as claimed in claim 1, wherein said buried layer is made of a material selected from a group consisting of GaAs and AlGaAs.
11. The semiconductor laser as claimed in claim 1, wherein said buried layer includes a layer which is made of a material having a energy band gap which is sufficiently wide such that a potential wall for blocking injection minority carriers is generated.
12. The semiconductor laser as claimed in claim 1, wherein said substrate is made of p-type InP, and said double heterostructure includes a first cladding layer, an active layer formed on the first cladding layer and a second cladding layer formed on the active layer, said first and second cladding layers being made of mutually opposite conductor types.
13. The semiconductor laser as claimed in claim 12, wherein said active layer is made of InGaAsP, said first cladding layer is made of p-type InP, and said second cladding layer is made of n-type InP.
14. The semiconductor laser as claimed in claim 13, wherein said buried layer is made of a material selected from a group consisting of n-type InGaAs and n-type AlInAs.
15. The semiconductor laser as claimed in claim 12, wherein said active layer is made of InGaAs, said first cladding layer is made of p-type AlInAs, and said second cladding layer is made of n-type AlInAs.
16. The semiconductor laser as claimed in claim 15, wherein said buried layer is made of a material selected from a group consisting of n-type InGaAs and n-type AlInAs.
17. The semiconductor laser as claimed in claim 15, which further comprises a p-type InP buffer layer interposed between said p-type InP substrate and said first cladding layer.
18. The semiconductor laser as claimed in claim 1, wherein said stripe of the first mesa includes a tapered part where a width along the <110> direction of the sloping surface which is approximately the (111)B face decreases towards an edge surface of the semiconductor laser.
19. The semiconductor laser as claimed in claim 18, wherein said stripe of the first mesa includes a prism shaped part which does not have the (100) face and terminates at the edge surface of the semiconductor laser.
20. The semiconductor laser as claimed in claim 19, wherein said prism shaped part has a height which is lower than a height of the (100) face at the type surface of the stripe of the first mesa.
21. The semiconductor laser as claimed in claim 1, wherein said buried layer completely covers the (111)B face of the stripe of the first mesa.
This is a division of application Ser. No. 07/892,680, filed Jun. 4, 1992 now U.S. Pat. No. 5,202,285, which in turn is a continuation of application Ser. No. 07/691,620, filed Apr. 25, 1991, now abandoned.
Various structures for controlling the mode of the semiconductor laser have been proposed and reduced to practice. However, most of the proposed structures are made using the LPE and utilize the growth peculiarity of the LPE such as the anisotropy. Very few of the proposed structures use the peculiarity of the MOVPE. In addition, even when an attempt is made to make using the MOVPE the semiconductor laser having the structure which is intended to be made by the LPE, it is extremely difficult to make the semiconductor laser by the MOVPE due to the growth peculiarity of the MOVPE.
However, the loss per unit length is large because this ridge type structure uses the loss guide system. For this reason, the differential quantum efficiency ηd greatly deteriorates as the cavity length becomes longer as may be seen from the following formula, where ηi denotes the internal quantum efficiency, α denotes the waveguide loss, L denotes the cavity length, R denotes the reflectivity of the laser edge facet and ln denotes the function describing natural logarithm.
&#951;d =&#951;i �[(1/L)ln (1/R)]/[&#945;+(1/L)ln (1/R)]
Furthermore, in the AlGaInP system semiconductor laser, the energy band gap of the active layer is large and the voltage applied above and below the active layer is high during the operation. For example, the energy band gap of the InGaP active layer 23 is 1.85 eV or greater. Generally, the buried type structure suffers from a problem in that a leak current flows via the interface state at the interface between the mesa etched surface and the buried layer, and the rise of the operation voltage directly leads to the increase of the leak current. Moreover, since the buried layer 26 is formed on the layer which includes Al, the interface state exists at the interface between the mesa etched surface and the buried layer 26, making it difficult to reduce the leak current, and causes the decrease of the differential quantum efficiency ηd. In addition, because the stripe width W is made narrow for the transverse mode control, the light energy density increases when producing the high output, and there is a problem in that a catastrophical optical damage (COD) breakdown easily occurs.
Next, the shaped substrate type structure shown in FIG. 3 will be studied. The shaped substrate type structure does not use the loss guide system, but uses the waveguide structure of the index guide by bending the active layer so that a small loss is realized. In addition, there is no need to form a layer which includes Al on a layer which includes Al. Hence, when the peculiarity of the AlGaInP system material is considered, the shaped substrate type structure may be best suited for producing a large output.
FIG. 4 shows a cross section of an essential part of the semiconductor laser using the shaped substrate type structure produced by the etching. The semiconductor laser shown in FIG. 4 includes an n-type GaAs substrate 41, a p-type GaAs current confinement layer 42, an n-type AlGaInP cladding layer 43, an InGaP active layer 44, a p-type AlGaInP cladding layer 45, a p-type InGaP buffer layer 46, a p-type GaAs contact layer 47, a guided light pattern 48 and an absorbing part 49. W denotes the stripe width, 0 denotes the inclination angle of the current confinement layer 42, and d denotes the thickness of the cladding layer 43.
FIG. 5 shows the above selective growth of the GaAs layer. The semiconductor laser includes a GaAs substrate 51, a SiO2 layer 52 and a GaAs layer 53. As shown, the cross section of the GaAs layer 53 becomes hexagonal by the selective growth.
FIG. 8 shows a cross section of a structure for explaining the growth of the semiconductor layer on the conventional mesa which is formed by the etching and extends in the <110> direction. In FIG. 8, those parts which are the same as those corresponding parts in FIG. 7 are designated by the same reference numerals, and a description thereof will be omitted. In this case, the surface of the semiconductor layer 63 which is formed on the mesa stripe 61A has a index of crystal face (100). the mesa stripe
On the other hand, other types of semiconductor lasers have been proposed in Japanese Laid-Open Patent Applications No. 55-158689, No. 64-30287 and the like.
FIG. 10 shows a semiconductor laser proposed in the Japanese Laid-Open Patent Application No. 55-158689. This semiconductor layer includes an n-type GaAs substrate 920, a p-type Ga1-x Alx As current blocking layer 921, an n-type Ga1-x Alx As cladding layer 922, an n or p-type GaAs active layer 923, a p-type Ga1-x Alx As cladding layer 924, a p-type GaAs ohmic contact layer 925, a p mode electrode 926, an n side electrode 927, a triangular prism shaped mesa part 928, a damaged part 929 and a light emitting region 930.
On the other hand, FIG. 11 shows shows a semiconductor laser proposed in the Japanese Laid-Open Patent Application No. 64-30287. This semiconductor layer includes a p-type GaAs substrate 901, a stripe convex part 902, a p-type GaAs buffer layer 903, p-type AlGaAs cladding layers 904 and 906, a current blocking layer 905, an AlGaAs active layer 907, an n-type AlGaAs cladding layer 908, an n-type GaAs contact layer 909, an n side ohmic electrode 910 and a p side ohmic electrode 911.
This structure basically employs the same principle as the structure shown in FIG. 9, and the stripe width and the thickness of the cladding layer cannot be selected independently. This structure differs from that shown in FIG. 9, however, in that the stripe convex part 902 formed on the substrate 901 has a re-entrant mesa shape. The cladding layer 904 which is formed on the substreate 901 grows on the side surface of the re-entrant mesa of the stripe convex part 902 and on the (111)B face at the side surface of the conventional mesa at the upper part of the stripe convex part 902. However, when the side surface of the re-entrant mesa and the side surface of the conventional mesa in the stripe convex part 902 have completely different indexes of crystal face, it was found from the experiments conducted by the present inventors that the morphology of the cladding layer 904 at such side surfaces becomes extremely poor. The present inventors have also found from other experiments that the morphology of a layer is satisfactory when the layer is grown on a side surface which is made up of only the (111)B face on which the layer growth is slow. For the above described reasons, it is difficult to produce a smooth stripe structure in the semiconductor laser proposed in the Japanese Laid-Open Patent Application No. 64-30287. Furthermore, since the scattering loss is large, it is impossible to produce a large output from this semiconductor laser. It was also found from the experiments conducted by the present inventors that the side surface of the mesa is desirably made up solely of the (111)B face.
Another semiconductor laser having the mesa structure is also proposed in a Japanese Laid-Open Patent Application No. 64-32692. However, illustration and description thereof will be omitted in this specification because the proposed structure is basically similar to the structure shown in FIG. 11.
FIG. 7 is a cross sectional view showing an essential part of the conventional semiconductor laser when a semiconductor layer is grown on a shaped substrate which has a conventional mesa extending in the <110> direction formed by the etching;
FIG. 10 is a cross sectional view showing an essential part of a semiconductor laser proposed in a Japanese Laid-Open Patent Application No. 55-158689;
FIG. 11 is a cross sectional view showing an essential part of a semiconductor laser proposed in a Japanese Laid-Open Patent Application No. 64-30287;
FIG. 12 is a plan view showing a essential part of a GaAs substrate which is used to form a shaped substrate;
FIG. 16 is a cross sectional view of an essential part of a sample for explaining a case where a GaAs layer is grown on a GaAs substrate 71 having mesas 71A and 71B;
FIG. 17 is a cross sectional view of an essential part of a sample, for explaining a case where a SiO2 layer formed by, a sputtering is used;
FIG. 38A is a diagram for explaining a stacked structure at an essential part of the semiconductor laser shown in FIG. 37 in correspondence with the laser field intensity distribution FIG. 38(B);
FIGS. 54(A), 54(B) are cross sectional views showing essential parts of the semiconductor laser taken along lines c--c' and d--d' in FIG. 53;
FIGS. 66(A) and 66(B) are cross sectional views showing essential parts of the semiconductor laser taken along lines a1--a1' and b1--b1' in FIG. 61;
FIGS. 67(A) and 67(B) are cross sectional views showing essential parts of the semiconductor laser taken along lines a2--a2-- and b2--b2' in FIG. 63;
FIGS. 71(A) and 71(B) are cross sectional views showing essential parts of a semiconductor laser at various production stages of a fourth embodiment of the method of producing the semiconductor laser according to the present invention;
FIGS. 78(A) and 78(B) are cross sectional views for explaining double heterostructure which are formed at growth temperatures of 690� C. and 730� C.;
FIG. 12 is a plan view showing an essential part of a GaAs substrate which is used for the experiment to form a shaped substrate. A GaAs substrate 71 has a main surface which is the index of crystal surface (100). The <110> direction is perpendicular to the facet edge, and the <110 > is parallel to the facet edge. When a NH3 system etching solution is used on this GaAs substrate 71, a re-entrant mesa is formed in the <110> direction and a conventional mesa is formed in the <110> direction.
(c) Br/CH3 COOH:H3 PO4 FIG. 13 (A), (B) and (C) respectively show an essential part of a sample for explaining the formation of a mesa stripe in the <110> using the etching solutions (a), (b) and (c). In FIG. 13, the same designations are used as in FIG. 12. A stripe SiO2 layer 72 extends in the <110> direction. FIG. 13 (A) shows a state where the etching is made using the etching solution (a) at an etching speed of 2.5 μm/min, and the sloping surface of the re-entrant mesa is estimated to be the (221)A face. FIG. 13 (B) shows a state where the etching is made using the etching solution (b) at an etching speed of 2.5 μm/min. In this case, a small conventional mesa is formed at the bottom part, and the sloping surface of this small conventional mesa is estimated to be the (111)B face. FIG. 13 (C) shows a state where the etching is made using the etching solution (c) at an etching speed of 0.4 μm/min. In this case, the sloping surface of the conventional mesa is rounded and is estimated to be the (011) face.
FIGS. 14 (A), (B) and (C) respectively show an essential part of a sample for explaining the formation of a groove in the <110> using the etching solutions (a), (b) and (c). In FIG. 14, the same designations are used as in FIG. 13. The SiO2 layer 72 itself in this case does not have the stripe shape but has a stripe opening which extends in the <110> direction.
FIG. 17 shows an essential part of a sample for explaining a case where the SiO2 layer used is formed by the sputtering. In FIG. 17, the same designations as used as in FIGS. 12 through 16. A SiO2 layer 72, shown is formed by the sputtering. As may be seen from FIG. 17, the re-entrant mesa is completely eliminated, and the mesa structure is solely made up of the conventional mesa 71A.
FIG. 18 shows an essential part of a sample for explaining a case where a semiconductor layer is grown on the shaped substrate shown in FIG. 17. In FIG. 1B, the same designations are used as in FIGS. 12 through 17. As shown, a GaAs layer 73' is grown in this case, and the growth of this GaAs layer 73' extends to immediately under the SiO2 layer 72'. However, when the growth of the GaAs layer 73' is continued until the GaAs layer 73' becomes thick, the growth rate under the eaves of the SiO2 layer 72' slows down and a problem occurred in that a depression is formed as shown in FIG. 19.
FIG. 22 shows an essential part of a sample for explaining a state where the GaAs substrate 71 is etched using the RIE. In FIG. 22, the same designations are used as in FIGS. 12 through 21. As shown in FIG. 22, a sloping surface 71D of the mesa structure which is formed by the RIE is almost vertical. In addition, damages 76 are generated at the surface part of the substrate 71 due to the RIE.
The mixed solution of H2 SO4,H2 O2 and HF/NH4 F (BHF) is suited for use as the etchant when removing the eaves of the mask (SiO2 layer).
Thickness: 0.8 μm.
Impurity: Si.
Impurity concentration: 4�1017 cm-3.
Active layer 84
Thickness: 70 nm.
Thickness: 1.0 μm.
Impurity concentration: 3�1017 cm-3.
Buffer layer 86
Thickness: 100 nm.
Impurity: Zn.
Impurity concentration: 1�1018 cm-3.
Contact layer 87
Thickness: 2 μm.
Impurity concentration: 3�1018 cm-3.
As shown in FIG. 33, the insulator layer 88 made of SiO2 and having a thickness of 200 nm, for example, is formed on the contact layer 87 by a CVD. Then, the insulator layer 88 is etched to form a stripe opening using a resist process of a photolithography technique and a wet etching which uses a hydrofluoric acid buffer solution as the etchant.
A vacuum deposition is used to form on the contact layer 87 the p side electrode 89 which has a thickness of 4000 Å in total and is made up of stacked layers of Ti, Pt and Au. The Ti, Pt and Au layers respectively have thicknesses of 1000 Å , 1000 Å and 2000 Å.
Buried layer 102
Impurity concentration 3�1018 cm-3.
Buffer layer 103
Thickness: 0.1 μm.
Cladding layer 104
Thickness: 0.8 nm.
Impurity concentration: 1�1017 cm-3.
Active layer 105
Thickness: 1 nm.
n side electrode 108
Material: Au/AuGe (GaAs side).
Thickness: 2500 Å/500 Å.
Material: Au/Zn/Au (GaAs side).
Thickness: 2340 Å/360 Å/300 Å.
This embodiment differs from the third embodiment shown in FIG. 35 in that after the n-type GaAs buried layer 102 is formed, a p-type GaAs buffer layer 110 is formed prior to forming the p-type InGaP buffer layer 103. For example, the p-type GaAs buffer layer 110 has a thickness of approximately 300 Å and an impurity concentration of 3�1018 cm-3. According to this embodiment, it is possible to improve the morphology of the layers which are formed above the p-type GaAs buffer layer 110.
Next, a description will be given of a fifth embodiment of the semiconductor laser according to the present invention, by referring to FIG. 37. In this embodiment, the evanescent distribution of light in the n side cladding layer is made large. The semiconductor laser shown in FIG. 37 includes a p-type GaAs substrate 111, an n-type GaAs buried layer 112, a p-type GaAs buffer layer 113, a p-type InGaP buffer layer 114, a p-type AlInP cladding layer 115, an InGaP active layer 116, an n-type (Al0.5 Ga0.5)0.5 In0.5 P cladding (guide) layer 117, an n-type AlInP cladding layer 118, an n-type GaAs contact layer 119, an n side electrode 120 and a p side electrode 121. In this embodiment, the thickness and the like of each layer are as follows.
Impurity concentration: 1�1019 cm-3.
Buried layer 112
Buffer layer 113
Thickness: 300 Å.
Buffer layer 114
Cladding layer 115
Thickness: 0.4 μm.
Impurity concentration: 2�1017 cm-3.
Active layer 116
Thickness: 0.07 μm.
Thickness: 0.5 μm.
Cladding layer 118
Contact layer 119
n side electrode 120
In this embodiment, the evanescent distribution of light is increased by providing the n-type (Al0.5 Ga0.5)0.5 In0.5 P cladding layer 117 as the guide layer on the n side. At the same time, the D.C. resistance as a whole is reduced and it is possible to effectively suppress the temperature rise because the p-type AlInP cladding layer 115 having the large resistance can be made thin. According to the experiments conducted by the present inventors, it was found that the light absorption by the p-type GaAs substrate 111 or the p-type InGaP buffer layer 114 is light and the loss can be suppressed to a small value even when the thickness of the p-type AlInP cladding layer 115 is reduced to 0.4 μm. Moreover, it was also confirmed that the thermal resistance is effectively reduced because the p-type AlInP cladding layer 115 is thin and the InGaP active layer 117 is close to the n-type GaAs substrate 111.
The above described problem of the large power consumption may be reduced by providing a layer which is made of a material having an intermediate energy band gap between those of the GaAs and AlGaInP. Particularly, it is known to provide a buffer layer made of p-type InGaP or AlGaInP, for example, so as to confine the current using the characteristic of the buffer layer. For example, a semiconductor laser applied with such a current confinement structure is proposed in Japanese Laid-Open Patent Applications No. 62-200784 and No. 63-81884.
In order to overcome the problem caused by the p-type InGaP buffer layer 114, the current spread should be limited and the n-type GaAs buried layer should make direct contact with a p-type AlGaInP cladding layer 115, at only the current confinement part.
Next, a description will be given of a sixth embodiment of the semiconductor laser according to the present invention in which the structure of the p-type InGaP buffer layer 114 is modified, by referring to FIG. 44. In FIG. 44, those parts which are the same as those corresponding parts in FIGS. 37 and 41 are designated by the same reference numerals, and a description thereof will be omitted. In this embodiment, a p-type InGaP buffer layer 122 is provided.
In FIG. 47, a buried layer 123 is made of n-type AlGaAs, but it is also possible to use n-type AlGaInP in place of the n-type AlGaAs. However, the semiconductor laser shown in FIG. 47 suffers from the following problems.
Buried layer 125
Thickness: 500 to 1000 Å.
Buried layer 126
FIG. 49 shows an energy band diagram taken along a line Y--Y in FIG. 48. In FIG. 49, the same designations are used as in FIGS. 43 through 45 and 48.
FIG. 54 (A) shows a cross section taken along a line c--c, in FIG. 53, and FIG. 54 (B) shows a cross section taken along a line d--d' in FIG. 53. Since the (111)A face of the p-type GaAs substrate 101 is exposed at the part where the stripe width becomes large as shown in FIG. 54 (B), the n-type GaAs buried layer 102 grows and forms a shape which projects upwardly. For this reason, it becomes extremely difficult to control the shape of the double heterostructure which is formed above the structure shown in FIG. 54 (B).
FIG. 58 shows a tenth embodiment of the semiconductor laser according to the present invention A description will be given of a second embodiment of the method of producing the semiconductor laser according to the present invention for producing the tenth embodiment of semiconductor laser, by referring to FIGS. 55 through 58. In FIGS. 55 through 58, those parts which are the same as those corresponding parts in FIG. 36 are designated by the same reference numerals, and a description thereof will be omitted.
First, the structure shown in FIG. 55 is formed by carrying out processes similar to those described in conjunction with FIGS. 27 through 29. In other words, the SiO2 layer 91 is formed on the (100) face of the p-type GaAs substrate 101 by a sputtering. The normal photolithography technique is used to form a stripe pattern by a patterning. This stripe pattern has a wide part 91A which has a width of 9 μm, for example, and a narrow part 91B which has a width of 6 μm, for example, where the widths are taken along the <110> direction. The wide part 91A and the narrow part 91B are connected by a tapered part 91C which has a length of approximately 50 μm. The resist pattern which is used for this patterning is used as a mask when etching the SiO2 layer 91 by a hydrofluoric acid buffer solution, and the resist is thereafter removed. Next, the SiO2 layer 92 is used as a mask to etch the p-type GaAs substrate 101 by a mixed etchant of H.sub. 2 SO4 +H2 O2 +H2 O which is heated to approximately 50� C., so as to remove approximately 2 μm of the SiO2 layer 91. As a result, approximately the (111)B face appears at the mesa side surface, and the top surface of the mesa structure has a wide part 101A having a width of approximately 4.8 μm and a narrow part 101B having a width of approximately 1.8 μm, where the widths are taken along the <110> direction.
Therefore, according to the present invention, it is simply necessary to form the n-type GaAs buried layer 102 so as to prevent insufficient coverage thereby. The excess coverage by the n-type GaAs buried layer 102 is positively prevented by the newly formed eaves of the SiO2 layer 91 As may be seen from FIG. 76, the growth of the n-type GaAs buried layer 102 stops at the bottom surface of the eaves of the SiO2 layer 91, and thus, it is possible to obtain the desired conventional mesa while preventing the (111)B face from being exposed.
As shown in FIG. 78 (A), substantially all of the InGaP active layer 1:5 is formed on the trapezoidal mesa structure via the p-type AlGaInP cladding layer 104 which is thicker than the n-type AlGaInP cladding layer 106 when the growth temperature is 690� C. But the thermal conductivity of the AlGaInP system material is small because it is a 4-element mixed crystal. For this reason, when substantially all of the InGaP active layer 105 makes contact with the p-type AlGaInP cladding layer 104 which is thicker than the n-type AlGaInP cladding layer 106, it is impossible to efficiently release the heat generated from the InGaP active layer 105 to the GaAs trapezoidal mesa part, and the output saturation of the semiconductor laser occurs due to the heat when the semiconductor laser is operated to produce a large output.
In FIG. 82, the remaining SiO2 layer is used as a mask and an MOVPE is used to grow the n-type GaAs buried layer 102 to a thickness of 0.9 μm, for example. The impurity of the n-type GaAs buried layer 102 is Si, and the impurity concentration is 3�1018 cm-3, for example. Hence, a trapezoidal mesa having the (311)B face as its sloping surface is formed.
In FIG. 85, the p side electrode 109 is formed by successively stacking Au/Zn/Au by vacuum deposition. Similarly, the n side electrode 108 is formed by successively stacking Au/AuGe by vacuum deposition. Thereafter, the electrodes 109 and 108 are alloyed at 430� C., and the semiconductor laser is completed by forming a cavity length of 300 μm, for example. The semiconductor laser which is completed is basically the same as the semiconductor laser shown in FIG. 36.
When the growth temperature becomes high, it becomes difficult to reduce the resistance of the p-type layer in the case of the AlGaInP/GaInP system material. Hence, it is necessary to inject the p-type impurities with a high dosage, but in this case, the change in the junction position due to the diffusion of the p-type impurities during the growth process no longer becomes negligible. Accordingly, the growth temperature is desirably in the range of 710� to 750� C.
In FIG. 86, an insulator layer 202 made of SiO2, for example, is formed on a GaAs substrate 201. The insulator layer 202 is etched to form a stripe opening 202A in the <110> direction of the GaAs substrate 201.
In FIG. 89, a chemical vapor deposition (CVD) is used to form a SiO2 insulator layer 206 having a thickness of approximately 2000 Å, for example, on an n-type GaAs substrate 205. The insulator layer 206 may of course be made of a material other than SiO2, such as SiN.
Material: p-type GaAs.
Material n-type AlGaInP.
Impurity concentration: 7�1017 cm-3.
Material: Non-doped InGaP.
Material: p-type AlGaInP.
In FIG. 94, a low pressure MOVPE is used to grow the n-type GaAs layer 207 on the n-type GaAs substrate 205 which is exposed within the stripe opening 206A. When the stripe opening 206A has the width of 3 μm, the cross section of the grown n-type GaAs layer becomes trapezoidal as shown when the growth temperature is 690� C. and the growth time is 15 minutes. The sloping surface of the n-type GaAs layer 207 is the (111)B face, and the maximum thickness (height) of the n-type GaAs layer 207 is 1.5 μm.
Material: n-type AlGaInP.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS4506366 *Jun 29, 1982Mar 19, 1985Hitachi, Ltd.Semiconductor laser deviceUS4692927 *Mar 15, 1985Sep 8, 1987Hitachi, Ltd.Light emitting device with improved electrode structure to minimize short circuitingUS4701927 *Jan 25, 1985Oct 20, 1987Hitachi, Ltd.Light emitting chip and optical communication apparatus using the sameUS4757509 *Jul 23, 1986Jul 12, 1988Mitsubishi Denki Kabushiki KaishaSemiconductor laser apparatusUS4813050 *May 27, 1987Mar 14, 1989Mitsubishi Denki Kabushiki KaishaSemiconductor laser deviceUS4894840 *Jun 27, 1988Jan 16, 1990Massachusetts Institute Of TechnologySurface emitting laserUS4932033 *Nov 17, 1988Jun 5, 1990Canon Kabushiki KaishaSemiconductor laser having a lateral p-n junction utilizing inclined surface and method of manufacturing sameUS4940672 *Mar 17, 1989Jul 10, 1990Kopin CorporationMethod of making monolithic integrated III-V type laser devices and silicon devices on siliconUS4974232 *Jul 21, 1989Nov 27, 1990Kabushiki Kaisha ToshibaSemiconductor laser deviceUS4984244 *Sep 13, 1989Jan 8, 1991Sharp Kabushiki KaishaSemiconductor laser deviceUS4994143 *Apr 2, 1990Feb 19, 1991Electronics And Telecommunications Research InstituteMethod for manufacturing a buried heterostructure laser diodeEP0136097A2 *Aug 29, 1984Apr 3, 1985Sharp Kabushiki KaishaMethod for the production of semiconductor lasersEP0234955A2 *Feb 27, 1987Sep 2, 1987Kabushiki Kaisha ToshibaSemiconductor laser with mesa stripe waveguide structure and manufacturing method thereofJPH01313982A * Title not availableJPS5864085A * Title not availableJPS6381884A * Title not availableJPS6430287A * Title not availableJPS6432692A * Title not availableJPS55158689A * Title not availableJPS62200784A * Title not available* Cited by examinerNon-Patent CitationsReference1Kenneth M. Dzurko et al., "Low Threshold Quantum Well Lasers Grown by Metalorganic Chemical Vapor Deposition on Nonplanar Substrates", IEEE Journal of Quantum Electronics. New York: Jun. 1989.2 *Kenneth M. Dzurko et al., Low Threshold Quantum Well Lasers Grown by Metalorganic Chemical Vapor Deposition on Nonplanar Substrates , IEEE Journal of Quantum Electronics. New York: Jun. 1989.* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS5375136 *Apr 11, 1994Dec 20, 1994Fujitsu LimitedSemiconductor laser of patterned-substrate type and structure thereofUS5418374 *Jun 2, 1993May 23, 1995Sony CorporationSemiconductor device having an active layer with regions with different bandgapsUS5568500 *Mar 15, 1994Oct 22, 1996Fujitsu LimitedSemiconductor laserUS5814531 *Jan 29, 1996Sep 29, 1998Fujitsu LimitedMethod for forming semiconductor laser emitting light from slant planeUS6019840 *Jun 27, 1997Feb 1, 2000The Board Of Trustees Of The University Of IllinoisProcess for forming deep level impurity undoped phosphorous containing semi-insulating epitaxial layersUS6865205 *May 15, 2002Mar 8, 2005Matsushita Electric Industrial Co., Ltd.Semiconductor laserUS7221692 *May 13, 2004May 22, 2007Kabushiki Kaisha ToshibaSemiconductor laser device and its manufacturing methodUS7259406 *Nov 2, 2005Aug 21, 2007Mitsubishi Denki Kabushiki KaishaSemiconductor optical elementUS20050030997 *May 13, 2004Feb 10, 2005Akira TanakaSemiconductor laser device and its manufacturing methodUS20060220037 *Nov 2, 2005Oct 5, 2006Mitsubishi Denki Kabushiki KaishaSemiconductor optical element* Cited by examinerClassifications U.S. Classification372/46.01, 372/45.01International ClassificationH01S5/227, H01S5/16, H01S5/10, H01S5/32, H01S5/223, H01S5/343, H01S5/323, H01S5/22, H01L33/00Cooperative ClassificationH01S5/2201, H01S5/2206, H01L33/0062, H01S5/10, H01S5/32391, H01S5/3211, B82Y20/00, H01S5/34326, H01S5/2232, H01S5/2209, H01S5/2272, H01S5/2235, H01S5/32325, H01S5/221, H01S5/16, H01S5/1064European ClassificationB82Y20/00, H01S5/223D, H01S5/323B2, H01S5/343E, H01L33/00G3, H01S5/10, H01S5/16Legal EventsDateCodeEventDescriptionMay 27, 1997REMIMaintenance fee reminder mailedOct 19, 1997LAPSLapse for failure to pay maintenance feesDec 30, 1997FPExpired due to failure to pay maintenance feeEffective date: 19971022RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services