THE SEMICONDUCTOR LED DEVICE AND PRODUCING METHOD

Abstract: The present invention provides a semiconductor device with InxGal-xN crystal passivation layer and manufacturing method thereof which effectively blocks the leakage current between the surface and boundary of a device and a pn-junction boundary, and enhances the light emission efficiency as forming new structural semiconductor devices by removing the conventional dielectric passivation layer and using InxGal-xN crystal layer instead. A semiconductor device with gallium nitride type crystal passivation layer, wherein said semiconductor device has a p-n junction diode construction and forms an InxGal-xN crystal passivation layer with a specified thickness and a width around the edge of the upper surface of p-GaN layer which is the top layer of the semiconductor device.

Description: THE SEMICONDUCTOR LED DEVICE AND PRODUCING METHOD TECHNICAL FIELD The present invention is related to semiconductor devices and manufacturing methods thereof. More particularly, the invention relates to a semiconductor device and manufacturing methods thereof with gallium nitride type crystal passivation layer and manufacturing method thereof which improves the effectiveness for blocking leakage current and theraial emission efficiency by using InxGal-xN crystal body instead of the conventional dielectric passivation layer. BACKGROUND ART As shown in FIG. 1 , a GaN type Light Emitting Diode(LED) generally comprises a buffer layer 11 on a sapphire substrate 10, a n-type GaN layer 12, a InGaN(or GaN) active layer 13, a p-type GaN layer 14, a transparent electrode 15, a dielectric passivation layer 16, a n-type metal electrode 17 and a p-type metal electrode 18. The method of forming a GaN type Light Emitting Diode(LED) comprises the steps of successively crystal growing of a buffer layer 11 on a sapphire substrate 10, a n-type GaN layer 12, a InGaN(or GaN) active layer 13, and a p-type GaN layer 14 according to the Metal Organic Chemical Vapor Deposition(MOCVD) method; partly etching up to a n-type GaN layer 12 in order to form a n-type metal electrode 17; forming a transparent electrode 15; coating the surface with a dielectric passivation layer except the electrode region; and depositing a n-type metal electrode 17 and a p-type metal electrode 18. FIG. 2 is a cross-section diagram which illustrates the principle of leakage current occurrence for a GaN type optical semiconductor device in the absence of a dielectric passivation layer. As shown in FIG. 2, the leakage current flows through the surfaces and boundaries when a voltage is applied to the electrode teπninals and has significant effects on the performance of the device and sometimes causes destruction of the device. For the case of GaN type semiconductor devices, boundaries for electrode deposition of a device are fomied by Reactive Ion Etching (RIE). At this instance, the boundaries are damaged due to high energy ion bombardments and leakage current occurs along the damaged boundaries. Also, during the breaking or sawing of a device into individual chips after the completion of the process, a lot of stress exist on the cleavage boundary of the crystal growth layer and generally the boundaries become very rough due to the cleave not coinciding with the crystal faces. A large amount of leakage current flows along these rough boundaries. Accordingly, at the conventional GaN type semiconductor, as shown on FIG. 1, the leakage current is prevented by coating the surface between the p metal electrode 18 and n-GaN 12 with a dielectric passivation layer 16. The dielectric passivation layer 16 cuts off the passage of the leakage current that flows on the boundaries through the semiconductor surface and protects the surface of the devices from external damages. This is an essential process in order to protect the devices from surface damages and also secure the reliability of the devices as well as improving the assembly yield. This process is also a final stage process which requires an extreme caution. According to a construction method of the conventional dielectric passivation layer, a dielectric passivation layer such as SiO2 or Si3N4 is deposited using the PECVD or Sputtering process after forming a transparent electrode and n-type & p-type basic electrodes. In this case, generally plasma is used for the deposition instead of a simple CVD method or thermal deposition method both of which has a weak adhesion strength between the dielectric passivation layer and semiconductor surface. The plasma deposition method can improve the adhesion among the dielectric passivation layer, metal surface(transparent electrode) and semiconductor surface. However, the deposition of a dielectric passivation layer under a plasma environment might cause a damage on the performance of the devices since RF power and DC bias, which is necessary for formation of plasma, are directly applied to the surface of the semiconductor. Sometimes this damage on the performance of the devices might cause an eventual failure of the whole semiconductor process or a remarkable drop of the performance of the device. Also, since the dielectric passivation layer deposition process is the final process of the device manufacturing, the total yield and performance of the devices can be significantly affected by a small process variable. If an optical semiconductor device were to be operated at a high output mode due to high voltage and high current, the light emission efficiency of the device is lowered due to the theraial resistance characteristic(very low thermal resistance) of the dielectric which reduces the amount of themial emission generated by the InGaN active layer 13. Especially, in case of the junction-side down method which bonds a metal frame(or submount 19) with the upper face of the device for thermal emission as shown in FIG. 3, an inconsistent device, where a dielectric passivation layer 16 blocks in between the semiconductor device and metal frame 19, is constructed. Also, the amount of leakage current on the p-n diode junction boundary is not negligible and this significantly affects the reliability of the device. It is difficult to sufficiently recognize the leakage current at the initial stage since it affects device yield after an assembly and a long term reliability. Hence, it is required to fundamentally block the leakage current between a p metal electrode and n-GaN layer. DETAILED DESCRIPTION OF THE INVENTION The present invention is designed to overcome the above problems of prior art. The object of the invention is to provide new structural semiconductor devices which effectively blocks the leakage current between the surface & boundary of a device and a pn-junction boundary, and enhances the light emission efficiency by removing the conventional dielectric passivation layer accompanying several problems and using InxGal-xN crystal layer instead. Namely, the GaN type optical semiconductor device with a pn junction diode structure compraising a n-type electrodes, a transparent electrode and p-type electrodes according to the present invention is constructed first by sequentially forming a buffer layer on a substrate, a n-type GaN layer, a InGaN/GaN active layer, a p-type GaN layer and a n-InxGal-xN crystal layer, afterwards fomiing a n-InxGal-xN(0≤ x ≤l) crystal passivation layer with a specified thickness(t) and width (w) only around the edge of the upper surface of the p-GaN layer. The n-InxGal-xN(0≤ x ≤l) crystal passivation layer is grown with a thickness around 0.1 nm ≤ t < 5,000 nm. The value of n-doping concentration is lxlO 15 unit/cm 3 < n < lxlO 22 unit/cm 3 and the width is 0.1 μm < w < 300 μm. The present invention constructed as explained so far is to provide a semiconductor device and manufacturing methods thereof with gallium nitride(GaN) type crystal passivation layer has a new structural semiconductor in order to be used as leakage current block and device passivation layer, by using InxGal-xN crystal body is deposited at the initial crystal formation stage of the device instead of the conventional dielectric passivation layer which is deposited at the final process of the device. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross section diagram which shows a structure the conventional GaN type optical semiconductor device. FIG. 2 is a cross-section diagram which illustrates the principle of leakage current occurrence for a GaN type optical semiconductor device. FIG. 3 is a cross section diagram which shows a junction-side down type assembly structure for a high output operation of the conventional GaN type optical semiconductor device. FIG. 4 is a cross section diagram which shows one embodiment of the construction of optical semiconductor device with a n-InxGal-xN crystal passivation layer according to the present invention. FIG. 5a and 5b are cross-section diagrams of the main parts which illustrate the principle of cutting off the leakage current and pinch-off phenomena for the optical semiconductor device according to the present invention. FIG. 6a to FIG. 6e are cross section diagrams which illustrate the manufacturing process of the optical semiconductor device with a n-InxGal-xN crystal passivation layer according to the present invention. FIG. 7 is a cross section diagram which shows the principle of the photo electrochemical etching method adopted by the present invention. FIG. 8 is a cross section diagram which shows other embodiment of the construction of optical semiconductor device with a n-InxGal-xN crystal passivation layer according to the present invention. [Description of the numeric on the main parts of the drawings] 10, 40 : Substrate 11, 41 : Buffer Layer 12, 42 : n-GaN Layer 13. 43 : InGaN (or Gan) Active Layer 14. 44 : p-GaN Layer 15, 46 : Transparent Electrode 16 : Dielectric Passivation Layer 17, 47 : n Type Metal Electrode 18, 48 : p Type Metal Electrode 45-a : InxGal-xN Crystal Layer 45: InxGal-xN Crystal Passivation Layer BEST MODE FOR CARRYING OUT THE INVENTION In order to achieve the stated object, semiconductor device which forms the gallium nitride type crystal passivation layer according to the present invention has GaN type semiconductor device with a p-n junction diode structure comprises a InxGal-xN crystal layer with a specified thickness and width as a pssivation layer on the top edge region of a p-GaN layer which is at the upper most layer of the semiconductor device. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 4 shows one embodiment of the construction of optical semiconductor device with a InxGal-xN crystal passivation layer according to the present invention. As shown in FIG. 4, the GaN type optical semiconductor device with a pn junction diode structure compraising a n-type electrodes 47, a transparent electrode 46 and p-type electrodes 48 according to the present invention is constructed first by sequentially forming a buffer layer 41 on a substrate 40, a n-type GaN layer 42, a InGaN/GaN active layer 43, a p-type GaN layer 44 and a n-InxGal-xN crystal layer 45-a, afterwards forming a n-InxGal-xN(0≤ x ≤ l) crystal passivation layer 45 with a specified thickness(t) and width(w) only around the edge of the upper surface of the p-GaN layer 44. The n-InxGal-xN(0≤ x ≤ 1) crystal passivation layer 45 is grown with a thickness around 0.1 nm ≤ t < 5,000 nm. The value of n-doping concentration is lxlO 15 unit/cm 3 < n < lxlO 22 unit/cm 3 nit/cm 3 and the width is 0.1 μm < w < 300 μm. . The present invention constructed as explained so far is to provide a semiconductor device and manufacturing methods thereof with gallium nitride(GaN) type crystal passivation layer has a new structural semiconductor in order to be used as leakage current block and device passivation layer, by using InxGal-xN crystal body 45-a is deposited at the initial crystal formation stage of the device instead of the conventional dielectric passivation layer 16 which is deposited at the final process of the device. Hence, it is effective for cutting off the leakage current and is able to resolve many problems that come with depositing a dielectric passivation layer at the final stage. FIG. 5a and 5b illustrate the principle of cutting off the leakage current for the optical semiconductor device according to the present invention. As shown in FIG. 5a, if a voltage (+V) is applied to the P electrode 48, the device center region (region (I)), where the n-InxGal-xN passivation layer 45 is not formed, becomes p-n junction diode structure and operates normally, however, the edge of device surface region (region (II)), where the n-InxGal-xN passivation layer is formed, becomes n-p-n junction diode structure with n-InxGal-xN/p-GaN/n-InxGal-xN and no current flows. Also, as shown in FIG. 5b, if a voltage is applied to one part on the top n-InxGal-xN passivation layer, it takes a n-InxGal-xN/p-GaN/n-InGaN/n-GaN structure and becomes a reverse directional junction to n-p-n junction. Also, a depletion region forms on the junction of the p-GaN layer 44 due to the influence of a high concentration n layer at the top and bottom and a pinch-off phenomenon occurs where no hole current flows in the horizontal direction of the p-GaN layer 44 hence the leakage current in the horizontal direction can be completely blocked. Also, since the interface section between the p-GaN layer 44 and n-InxGal-xN passivation layer 45 has a complete crystal structure such as a single crystal, the leakage current can more completely be blocked in comparison to the conventional dielectric passivation layer deposition. Especially, in comparison to dielectric passivation layer 16, the n-InxGal-xN passivation layer 45 has a much better heat transfer characteristic and is a good quality crystal layer which is identical to the construction layer of the device, hence, the n-InxGal-xN passivation layer type is a very effective structure for thermal emission for the junction-side down type. While, FIG. 6a to FIG. 6e are cross section diagrams which illustrate the manufacturing process of the optical semiconductor device with a n-InxGal-xN crystal passivation layer according to the present invention. As shown in FIG. 6a, the manufacturing method of the optical semiconductor device with a n-InxGal-xN crystal passivation layer according to the present invention comprises the steps of successively crystal growing of a buffer layer 41 on a substrate(sapphire, SiC, GaN, Si, etc) 40, a n-type GaN layer 42, a InGaN/GaN active layer 43, a p-type GaN layer 44 and a n-InxGal-xN crystal layer 45 according to the Metal Organic Chemical Vapor Deposition(MOCVD) method. As a carrier gas for growing the MOCVD crystal, high purity hydrogen gas(H2) or nitrogen gas(N2) can be used. Especially, in case of growing n-InxGal-xN crystal, the n-InxGal-xN crystal quality can be improved by growing in a N2 gas environment which has a heavier mass value than H2. Next, as shown in FIG. 6b, in order to form an n-type electrode 47, the upper right end section of the device is etched down to the n-GaN layer 42. Also, after the above process, a n-InxGal-xN passivation layer is fomied by removing the whole n-InxGal-xN crystal layer 45-a by a etching process except the specified region defined by the passivation layer of the device (around the edge of device surface)(see FIG. 6c). In this way, the n-InxGal-xN passivation layer 45 forms around the top edge of the p-type GaN layer 44 in the form of a square band. At this instance, for the etching of the n-InxGal-xN crystal layer 45-a, RIE etching method, chemical etching, or photo electrochemical etching method can be used. Among the etching methods listed above, the chemical etching method is most advantageous since it can minimize the damages on the device surface. Specifically, the photo electro chemical etching method is capable of selectively etching the n-InxGal-xN crystal layer 45-a or p-GaN layer therefore the most suitable method for the present invention. While, FIG. 7 is a cross section diagram which illustrates the principle of the photo electro chemical etching method adopted by the present invention. As shown in FIG. 7, the standard photo electro chemical etching method generates electrons and holes by exposing the subjected etching part to a light with a bigger energy value than the band gap of the n-InxGal-xN crystal layer and reacts with a electrolytic solution (KOH + H2O) in order to etch rapidly the hole generated part. Also, according to the polarity of voltage applied to the electrolytic solution and crystal layer, either n-type or p-type can selectively be etched. Accordingly, by selecting the polarity of voltage and exposing the subjected etching part to a light, only the n-In(x)Ga(l-x)N crystal layer 45-a can be selectively etched against the p-GaN layer 44 and the etched semiconductor surface can remain in very good state without any damage or stress. Also, as shown in FIG. 6d, if necessary, the manufacturing process of the optical semiconductor device according to the present invention is completed by depositing a transparent electrode 46 or front face electrode on the upper section of the n-InxGal-xN passivation layer 45 and p-GaN layer 44 and forming a n metal electrode 47 and p metal electrode 48 as shown in FIG. 6e. If necessary, the n-In(x)Ga(l-x)N crystal layer 45-a on the p-GaN layer 44 can form a passivation layer 45 as an insulator which does not conduct electricity by intentionally dropping the doping process or undergoing a slight p-type doping. FIG. 8 is a cross section diagram which shows other embodiment of the construction of the optical semiconductor device with the n-InxGal-xN crystal passivation layer according to the present invention. As shown in FIG. 8, the optical semiconductor device can be constructed in the form where p-type electrode is not applied to the n-InxGal-xN passivation layer 45 by coating the transparent electrode 46 only on the p-GaN layer 44. It should be understood, however, that the detailed description and specific examples are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. INDUSTRIAL APPLICABILITY According to the present invention constructed as explained so far, leakage current can completely be blocked flows from the surface of the device to the boundary of the device during crystal growing stage and due to n-p-n type junction structure the pinch-off phenomenon is occurred on the cleavage boundary of the p-GaN layer by forming a InxGal-xN on the top surface edge region of a p-GaN layer, hence the reliability and the yield of the devices can be improved very greatly. Also, InxGal-xN passivation layer of the present invention has very excellent themial conductibility hence, to be operated at a high output mode light emission efficiency and reliability of the device can be improved. Also, due to n-InxGal-xN passivation layer of the present invention is formed at the initial crystal formation stage of the device, the conventional dielectric deposition process which is performed at the final process of the device is omitted hence, the simplification of the process and the yield of the devices can be improved very greatly.

Claims: WHAT IS CLAIMED IS : 1. A semiconductor device with gallium nitride type crystal passivation layer, wherein said semiconductor device has a p-n junction diode construction and forms a InxGal-xN(0≤ x < 1) crystal layer with a specified thickness and a width around the edge of the upper surface of p-GaN layer which is the top layer of said semiconductor device as a pssivation layer. 2. The semiconductor device as claimed in Claim 1, wherein said InxGal-xN crystal passivation layer is grown with a thickness around 0.1 nm - 5,000 nm and a width 1 S 99 around 0.1 μm - 300 μm and the value of n-dopmg concentration is 1x10 - 1x10 unit/cm 3 . 3. The semiconductor device as claimed in Claim 1, wherein said InxGal-xN crystal passivation layer is either not doped or slightly p-type doped. 4. The semiconductor device as claimed in Claim 1, wherein an electrode face is not coated on the upper section of said InxGal-xN crystal passivation layer. 5. A manufacturing method for a semiconductor device with gallium nitride type crystal passivation layer comprising the steps of ; a. growing a InxGal-xN (O≤ x < 1) crystal passivation layer on the surface of p-GaN layer which is the top layer of said semiconductor device, and b. forming a InxGal-xN crystal passivation layer around the edge of the upper surface of p-GaN layer by removing the center section of said InxGal-xN crystal layer through a etching process. 6. The method as claimed in Claim 5, wherein said InxGal-xN crystal layer is grown in a N2 gas environment according to the MOCVD crystal growing method. 7. The method as claimed in Claim 5, wherein said InxGal-xN crystal passivation layer is formed by selecting any one of the etching method among the RIE etching, chemical etching, or photo electrochemical etching methods.

Inventors: KIM CHANG-TAE, KIM, CHANG-TAE
Applicants: EPIVALLEY CO LTD, KIM CHANG TAE, EPIVALLEY CO., LTD., KIM, CHANG-TAE
Application year: 2001
Main classification: H01L33
IPC codes: H01L21, H01L33, H01S5