Semiconductor laser device and method of manufacturing the same

A semiconductor laser device includes a first cladding including gallium nitride (GaN) on a substrate, a light waveguide on the first cladding, a first contact pattern, a first SCH pattern, a first active pattern, a second SCH pattern, a second cladding and a second contact pattern sequentially stacked on the light waveguide, and first and second electrodes on the first and second contact patterns, respectively.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2018-0007323, filed on Jan. 19, 2018, in the Korean Intellectual Property Office (KIPO), the contents of which are herein incorporated by reference in their entirety.

BACKGROUND

Example embodiments relate to a semiconductor laser device and a method of manufacturing the same.

2. Description of the Related Art

When a laser diode (LD) device is formed on a silicon-on-insulator (SOI) substrate, heat generated from the LD device may not be discharged into a substrate due to a silicon oxide layer, and thus the LD device may be deteriorated.

SUMMARY

Example embodiments provide a semiconductor laser device having improved characteristics.

Example embodiments provide a method of manufacturing a semiconductor laser device having improved characteristics.

According to certain example embodiments, the disclosure is directed to a semiconductor laser device, comprising: a first cladding on a substrate, the first cladding including gallium nitride (GaN); a light waveguide on the first cladding; a semiconductor laser source structure on the light waveguide, the semiconductor laser source structure comprising a first contact pattern, a first separate confinement heterostructure (SCH) pattern, a first active pattern, a second SCH pattern, a second cladding, and a second contact pattern sequentially stacked on the light waveguide; and first and second electrodes on the first and second contact patterns, respectively.

According to certain example embodiments, the disclosure is directed to a semiconductor laser device, comprising: a first cladding on a substrate, the first cladding including gallium nitride (GaN); first and second light waveguides on the first cladding, the first and second light waveguides including silicon (Si) and titanium oxide (TiO2), respectively; first and second semiconductor laser source structures on the first and second light waveguides, respectively; first and second electrodes connected to the first semiconductor laser source structure; and third and fourth electrodes connected to the second semiconductor laser source structure.

According to certain example embodiments, the disclosure is directed to a method of manufacturing a semiconductor laser device, the method comprising: forming a first cladding on a substrate, the first cladding including gallium nitride (GaN); forming a light waveguide on the first cladding; forming a semiconductor laser source structure on the light waveguide, the semiconductor laser source structure comprising a first contact pattern, a first separate confinement heterostructure (SCH) pattern, an active pattern, a second SCH pattern, a second cladding, and a second contact pattern sequentially stacked on the light waveguide; and forming first and second electrodes on the first and second contact patterns, respectively.

DETAILED DESCRIPTION

Example embodiments will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings.

FIG. 1is a cross-sectional view illustrating a first semiconductor laser device in accordance with example embodiments.

Referring toFIG. 1, the first semiconductor laser device may include a first cladding110, a first light waveguide125, and a first semiconductor laser source structure sequentially stacked on a first substrate100. The first semiconductor laser device may further include a second cladding130covering each of opposite sidewalls of the first light waveguide125, a second substrate120containing the first light waveguide125and the second cladding130, and first and second electrodes272and274.

The first substrate100may be a semiconductor substrate, e.g., a silicon substrate, a germanium substrate, etc. In example embodiments, the first substrate100may be a silicon substrate having (111) crystal plane. The first substrate100may be doped with p-type or n-type impurities.

In example embodiments, the first cladding110may include a material having a refractive index less than that of silicon (Si) and a heat conductivity more than that of silicon oxide (SiO2). The first cladding110may include, e.g., single crystalline gallium nitride (GaN). In some embodiments, the first cladding110may be doped with, e.g., carbon (C) or iron (Fe), thereby increasing insulative properties of the first cladding110.

The second substrate120may be bonded to an upper surface of the first cladding110. The second substrate120may be a semiconductor substrate, e.g., a silicon substrate or a germanium substrate. In example embodiments, the second substrate120may be a silicon substrate having (100) crystal plane. Alternatively, the second substrate120may be a silicon substrate having (111) crystalline plane.

The first light waveguide125may be contained in the second substrate120. For example, the top and bottom surfaces of the first light waveguide125may be at the same vertical heights as the respective top and bottom surfaces of the second substrate120. The first light waveguide125may be formed on the upper surface of the first cladding110, and may have a bar shape extending in a first direction substantially parallel to an upper surface of the first substrate100. The bar shape may be, for example, an oblong block shape elongated in the first direction. The first light waveguide125may be formed by etching a portion of the second substrate120, and thus may include substantially the same material as that of the second substrate120. Thus, the first light waveguide125may include a semiconductor material, e.g., silicon, germanium, etc., and may include, e.g., silicon having (100) crystal plane. The first light waveguide125may have a higher refractive index than that of the first cladding110and the second cladding130.

The second cladding130may be contained in the second substrate120, and may cover each of opposite sidewalls of the first light waveguide125. For example, the top and bottom surfaces of the second cladding130may be at the same vertical heights as the respective top and bottom surfaces of the second substrate120. The second cladding130may be formed on the upper surface of the first cladding110, and may cover each of opposite sidewalls of the first light waveguide125in a second direction substantially perpendicular to the first substrate100. The second cladding130may include a material having a refractive index less than that of silicon of the first light waveguide125, e.g., silicon oxide (SiO2) or silicon nitride (SiN). Alternatively, the second cladding130may include air.

In example embodiments, the first semiconductor laser source structure may have a laser structure of separate confinement heterostructure (SCH). For example, the first semiconductor laser source structure may include a first contact pattern262, a first SCH pattern252, a first active pattern242, a second SCH pattern232, a third cladding222and a second contact pattern212sequentially stacked on the second substrate120, which contains the first light waveguide125and the second cladding130, each of which may include III-V group materials.

The first contact pattern262may include, e.g., indium phosphide (InP) doped with n-type impurities. The first contact pattern262may have a width in the second direction greater than that of a first semiconductor laser source structure including the first SCH pattern252, the first active pattern242, the second SCH pattern232, the third cladding222and the second contact pattern212sequentially stacked on the first contact pattern262. In example embodiments, the first contact pattern262and the first semiconductor laser source structure may extend in the first direction.

The first and second SCH patterns252and232may include a material having a refractive index less than that of the first active pattern242and more than that of the third cladding222. The first and second SCH patterns252and232may include a material doped with n-type impurities and p-type impurities, respectively. The first SCH pattern252may include, e.g., indium gallium aluminum arsenide (InGaAlAs) doped with n-type impurities, the first active pattern242may include, e.g., undoped indium gallium aluminum arsenide (InGaAlAs), and the second SCH pattern232may include, e.g., indium gallium aluminum arsenide (InGaAlAs) doped with p-type impurities.

In other example embodiments, the first semiconductor laser source structure may include a double heterostructure laser, a quantum well (QW) laser, a quantum cascade laser, an interband cascade laser, a distributed Bragg reflector (DBR) laser, etc.

The first and second electrodes272and274may be formed on the first and second contact patterns262and212, respectively. In example embodiments, the first electrode272may be spaced apart from the first semiconductor laser source structure in the second direction, and the second electrode274may overlap the first light waveguide125in a vertical direction substantially perpendicular to the upper surface of the first substrate100and may extend in the first direction. Each of the first and second electrodes272and274may include a conductive material, e.g., a metal, a metal nitride, etc.

A first current blocking region280may be a region of the first semiconductor laser source structure doped with protons, and may block paths of current applied by the first and second electrodes272and274. In example embodiments, the first current blocking region280may be formed in an upper portion of the first active pattern242, the second SCH pattern232and the third cladding222. In example embodiments, the first current blocking region280may extend in the first direction, and may not overlap the first light waveguide125in the vertical direction, the vertical direction being perpendicular to the first and second directions.

In the first semiconductor laser device, voltage may be applied to the first and second electrodes272and274so that current may be generated through structures between the first and second electrodes272and274, i.e., through the first contact pattern262, the first SCH pattern252, the first active pattern242, the second SCH pattern232, the third cladding222and the second contact pattern212. Paths of the current may be restricted by the first current blocking region280, with the current paths remaining within portions of the first active pattern242, the second SCH pattern232, the third cladding222and the second contact pattern212overlapping the first light waveguide125in the vertical direction. For example, the current paths may be prevented from extending into the first current blocking region280.

By the current, electrons and holes may be coupled with each other to generate laser in the first active pattern242between the first contact pattern262and the first SCH pattern252doped with n-type impurities and the second SCH pattern232, the third cladding222and the second contact pattern212doped with p-type impurities, and the generated laser may move to the underlying first light waveguide125. The first light waveguide125may include a material having a refractive index more than that of the second cladding130that covers each of opposite sidewalls of the first light waveguide125or that of the first cladding110that covers a bottom of the first light waveguide125. For example, the generated laser may be guided by the first light waveguide125to move in the first direction, which may be the extension direction of the first light waveguide125.

In example embodiments, the first cladding110may include a material having a high heat conductivity, e.g., gallium nitride (GaN), and thus the heat generated from the first semiconductor laser source structure may be effectively discharged into the first substrate100. Accordingly, the deterioration of characteristics of the first semiconductor laser device due to heat may be enhanced, when compared to the conventional semiconductor laser device on an SOI substrate.

FIGS. 2 to 5are cross-sectional views illustrating a method of manufacturing the first semiconductor laser device in accordance with example embodiments.

Referring toFIG. 2, a first cladding110and a second substrate120may be sequentially formed on a first substrate100. For example, the first cladding110may be formed on the first substrate100, contacting the first substrate100, and the second substrate120may be formed on the first cladding110, contacting the first cladding110.

The first substrate100may be a semiconductor substrate, e.g., a silicon substrate, a germanium substrate, etc. In example embodiments, the first substrate100may be a silicon substrate having (111) crystal plane. The first substrate100may be doped with p-type or n-type impurities.

In example embodiments, the first cladding110may include a material having a refractive index less than that of silicon (Si) and a heat conductivity more than that of silicon oxide (SiO2). The first cladding110may include, e.g., single crystalline gallium nitride (GaN). The first cladding110may be formed by, e.g., a metal organic chemical vapor deposition (MOCVD) process on the first substrate100.

The second substrate120may be a semiconductor substrate, e.g., a silicon substrate, a germanium substrate, etc. In example embodiments, the second substrate120may be a silicon substrate having (100) crystal plane. Alternatively, the second substrate120may be a silicon substrate having (111) crystal plane.

The second substrate120may be formed on the first cladding110by bonding. After bonding the second substrate120on the first cladding110, an upper portion of the second substrate120may be removed so that the thickness of the second substrate120may be reduced. The upper portion of the second substrate120may be removed by, e.g., an etching process or a grinding process.

Referring toFIG. 3, the second substrate120may be partially removed to form a first opening exposing an upper surface of the first cladding110, and a second cladding130may be formed to fill the first opening.

The first opening may be formed by an etching process using an etching mask (not shown) on the second substrate120. In example embodiments, the first opening may extend in a first direction substantially parallel to an upper surface of the first substrate100, and may include two first openings formed to be spaced apart from each other in a second direction substantially parallel to the upper surface of the substrate100and substantially perpendicular to the first direction.

A portion of the second substrate120remaining between the two first openings may form a first light waveguide125, which may have a bar shape extending in the first direction. The bar shape may be, for example, an oblong block shape elongated in the first direction.

The second cladding130may be formed by forming a second cladding layer on the second substrate120to fill the first openings, and planarizing the second cladding layer until an upper surface of the second substrate120is exposed. The planarization process may include, e.g., a chemical mechanical polishing (CMP) process and/or an etching process. Top surfaces of the first light waveguide125, the second cladding130, and the second substrate120may be at substantially the same vertical level.

The second cladding130may include a material having a refractive index less than that of the first light waveguide125, e.g., silicon oxide (SiO2) or silicon nitride (SiN). Alternatively, the second cladding130may include air, and in this case, the formation process of the second cladding layer to fill the first opening may be skipped.

Referring toFIG. 4, a second contact layer210, a third cladding layer220, a second SCH layer230, a first active layer240, a first SCH layer250and a first contact layer260may be sequentially formed on a third substrate200.

The third substrate200may serve as a handling substrate, and may include a semiconductor material, e.g., silicon, or an insulation material, e.g., glass.

Each of the second contact layer210, the third cladding layer220, the second SCH layer230, the first active layer240, the first SCH layer250and the first contact layer260may include III-V group materials.

In example embodiments, each of the first and second SCH layers250and230may include a material having a refractive index less than that of the first active layer240and more than that of the third cladding layer220. The first SCH layer250and the first contact layer260may include a material doped with n-type impurities, and the second contact layer210, the third cladding layer220and the second SCH layer230may include a material doped with p-type impurities.

Referring toFIG. 5, after turning over the third substrate200(i.e., rotating by 180 degrees), the third substrate200and the second substrate120may be bonded with each other, so that the first contact layer260contacts an upper surface of the second substrate120at which the first light waveguide125and the second cladding130are formed. For example, the first contact layer260and the upper surface of the second substrate120may be in contact with one another at the areas of the second substrate200surrounding the first light waveguide125and the second cladding130.

Thus, a first semiconductor laser source structure layer including the first contact layer260, the first SCH layer250, the first active layer240, the second SCH layer230, the third cladding layer220and the second contact layer210sequentially stacked may be formed on the second substrate120.

Referring toFIG. 1again, the second contact layer210, the third cladding layer220, the second SCH layer230, the first active layer240and the first SCH layer250may be patterned to form a second contact pattern212, a third cladding222, a second SCH pattern232, a first active pattern242and a first SCH pattern252, respectively, and the first contact layer260may be also patterned to form a first contact pattern262. Thus, a first semiconductor laser source structure including the first contact pattern262, the first SCH pattern252, the first active pattern242, the second SCH pattern232, the third cladding222and the second contact pattern212sequentially stacked may be formed on the second substrate120.

The first contact pattern262may have a width in the second direction greater than that of a first semiconductor laser source structure including the first SCH pattern252, the first active pattern242, the second SCH pattern232, the third cladding222and the second contact pattern212. Each of the first contact pattern262and the first semiconductor laser source structure may extend in the first direction.

First and second electrodes272and274may be formed on the first and second contact patterns262and212, respectively. In example embodiments, the first electrode272may be spaced apart from the first semiconductor laser source structure in the second direction, and the second electrode274may overlap the first light waveguide125in a vertical direction substantially perpendicular to the upper surface of the first substrate100and extend in the first direction. The first and second electrodes272and274may include, e.g., a metal, a metal nitride, etc.

Protons may be implanted into the first semiconductor laser source structure by an ion implantation process to complete the fabrication of the first semiconductor laser device.

In example embodiments, the protons may be doped into the first semiconductor laser source structure using the second electrode274as an ion implantation mask, and may pass through the second contact pattern212to reach a portion of the first active pattern242. For example, the protons may be doped into an upper portion of the first active pattern242, the second SCH pattern232and the third cladding222, so as to form a first current blocking region280. In example embodiments, the first current blocking region280may extend in the first direction, and may not overlap the first light waveguide125in the vertical direction.

FIG. 6is a cross-sectional view illustrating a second semiconductor laser device in accordance with example embodiments. The second semiconductor laser device may be substantially the same as or similar to the first semiconductor laser device, except that the second semiconductor laser device further includes a second active pattern. Thus, like reference numerals refer to like elements, and detailed descriptions thereon are omitted herein.

Referring toFIG. 6, the second semiconductor laser device may further include a second active pattern115in the first cladding110. For example, the second active pattern115may be formed between upper and lower portions of the first cladding110, and the upper and lower portions of the first cladding110may sandwich the second active pattern115.

The second active pattern115may include, e.g., indium gallium nitride (InGaN), indium aluminum gallium nitride (InAlGaN), aluminum nitride (AlN), etc., and may have a thin thickness as a quantum well (QW).

When the second active pattern115is formed, a third electrode (not shown) may be further formed beneath the first substrate100, and laser may be generated in the second active pattern115by current between the third electrode and the first electrode272, as in the first active pattern242. The generated laser may move to the overlying first light waveguide125, and may be guided by the first light waveguide125to move in the first direction. Thus, the second active pattern115may serve as a modulator for modulating the generated laser in the first active pattern242.

FIG. 7is a cross-sectional view illustrating a third semiconductor laser device in accordance with example embodiments. The third semiconductor laser device may be substantially the same as or similar to the first semiconductor laser device, except that the third semiconductor laser device includes a second light waveguide instead of the first light waveguide. Thus, like reference numerals refer to like elements, and detailed descriptions thereon are omitted herein.

Referring toFIG. 7, the third semiconductor laser device may include the first cladding110, a second light waveguide290and a second semiconductor laser source structure sequentially stacked on the first substrate100. The third semiconductor laser device may further include the second cladding130covering each of opposite sidewalls of the second light waveguide290, the second substrate120containing the second light waveguide290and the second cladding130, and fourth and fifth electrodes276and278.

A bottom of the second light waveguide290may be covered by the first cladding110, and each of opposite sidewalls of the light waveguide290in the second direction may be covered by the second cladding130. In example embodiments, the second light waveguide290may include, e.g., titanium oxide (TiO2). Titanium oxide of the second light waveguide290may have an absorption coefficient of light less than that of silicon of the first light waveguide125in a short wavelength range, and thus may serve as a light waveguide with less or no light loss. For example, the first light waveguide125ofFIG. 1may be used in a long wavelength range of about 1100 nm to about 1600 nm, and the second light waveguide290ofFIG. 7may be used in a short wavelength range of about 300 nm to about 500 nm.

In the third semiconductor laser device including the second light waveguide290, the first cladding110may include, e.g., silicon oxide of the conventional SOI substrate instead of gallium nitride (GaN).

The second semiconductor laser source structure may have a SCH laser structure the same as that ofFIG. 1. For example, the second semiconductor laser source structure may include a third contact pattern264, a third SCH pattern254, a third active pattern244, a fourth SCH pattern234, a fourth cladding224and a fourth contact pattern214sequentially stacked on the second substrate120containing the second light waveguide290and the second cladding130, each of which may include III-V group materials, and a second current blocking region285may be formed in an upper portion of the third active pattern244, the fourth SCH pattern234and the fourth cladding224. The third contact pattern264, the third SCH pattern254, the third active pattern244, the fourth SCH pattern234, the fourth cladding224and the fourth contact pattern214may be formed of the same materials and in the same manner as the first contact pattern262, the first SCH pattern252, the first active pattern242, the second SCH pattern232, the third cladding222and the second contact pattern212, respectively, as described in connection withFIGS. 1-5. Likewise, the second current blocking region285may be formed of the same materials and in the same manner as the first current blocking region280, as described in connection withFIGS. 1-5.

FIG. 8is a cross-sectional view illustrating a fourth semiconductor laser device in accordance with example embodiments. The fourth semiconductor laser device includes the first semiconductor laser device ofFIG. 1and the third semiconductor laser device ofFIG. 7on the first substrate100and the first cladding110. Thus, like reference numerals refer to like elements, and detailed descriptions thereon are omitted herein.

Referring toFIG. 8, the fourth semiconductor laser device may include the first cladding110and the second substrate120sequentially stacked on the first substrate100including first and second regions I and II.

Additionally, the fourth semiconductor laser device may include the first light waveguide125and the first semiconductor laser source structure sequentially on the first region I of the first substrate100, the second cladding130contained in the second substrate120and covering each of opposite sidewalls of the first light waveguide125, and the first and second electrodes272and274. The fourth semiconductor laser device may further include the second light waveguide290and the second semiconductor laser source structure sequentially on the second region II of the first substrate100, the second cladding130contained in the second substrate120and covering each of opposite sidewalls of the second light waveguide290, and the fourth and fifth electrodes276and278.

In example embodiments, the first and second light waveguides125and290and the first and second semiconductor laser source structures may be formed on the same first substrate100, and thus carbon (C) or iron (Fe) may be doped into the first cladding110so as to increase the insulation property of the first cladding110.

As illustrated above, the first light waveguide125on the first region I of the first substrate100may guide light in a relatively long wavelength range (e.g., about 1100 nm to about 1600 nm), and the second light waveguide290on the second region II of the first substrate100may guide light in a relatively short wavelength range (e.g., 300 nm to about 500 nm).