Nitride-based electronic device having an oxide cladding layer and method of production

A nitride-based electronic device includes an oxide cladding layer, a nitride cladding layer, and a nitride active region layer arranged between the oxide cladding layer and the nitride cladding layer. First and second metal contacts are electrically coupled to the nitride active region layer. The nitride-based electronic device can be formed in a system in which a non-reactive chamber is arranged between an oxide reaction chamber and a nitride reaction chamber so that oxide and nitride layers can be grown without exposing the device to the environment between growth of the oxide and nitride layers.

BACKGROUND

Technical Field

Embodiments of the subject matter disclosed herein generally relate to a nitride-based electronic device having an oxide cladding layer and method of production of such a device.

Discussion of the Background

Nitride-based electronic devices are typically produced using a metal organic chemical vapor deposition (MOCVD) system. For example, nitride-based light emitting diodes (LEDs) and lasers are typically formed by supplying p- and n-type nitride-based semiconductor gasses into a metal organic chemical vapor deposition system.

FIG. 1illustrates a cross-sectional view of a laser formed using a metal organic chemical vapor deposition system. The device includes a bottom metal contact105, on which an n-type gallium nitride (GaN) substrate110is formed. A n-type aluminum gallium nitride (AlGaN) cladding layer115is formed on the n-type gallium nitride substrate110, and an n-type gallium nitride waveguide layer120is formed on the cladding layer115. A nitride active region layer125comprising indium gallium nitride (InGaN) or gallium nitride is formed as multiple-quantum-wells (MQWs) on the waveguide layer120.

The other side of the nitride active region layer125generally mirrors the layers below except that the layers below the nitride active region layer125that are n-type are p-type above the nitride active region layer125. Specifically, a p-type gallium nitride waveguide layer130is formed on the nitride active region layer125and a p-type aluminum gallium nitride cladding layer135is formed on the p-type waveguide layer130. A p-type gallium nitride contact layer140is formed on the cladding layer135and a metal contact145is formed on the p-type contact layer140.

In the device ofFIG. 1, the n-type120and p-type130waveguide layers direct the energy (i.e., light or laser energy) produced by the nitride active region layer125horizontally. These waveguide layers120and130, however, do not completely prevent vertical leakage of the energy, which is why the device100includes relatively thick cladding layers115and135.

The p-type layers130-140are formed using magnesium (Mg) as a dopant fed into the metal organic chemical vapor deposition system while the respective nitride gasses are fed into the system. The p-type cladding layer135exhibits a low refractive index, which confines light in the waveguide layers120and130. Further, these p-type layers are relatively highly resistive compared to the n-type layers and also have a lot of crystal defects. The high resistivity results in high operation voltage of the electronic device, which means the electronic device also has low wall-plug efficiency. Accordingly, only a part of the operation voltage is applied to the p-type regions and the extra bias enhances degradation of the device, which reduces the device lifetime. The crystal defects in the p-type layers degrade the performance of the device and/or the lifetime of the device.

Thus, it would be desirable to provide a nitride-based electronic device with a cladding layer exhibiting at least the same low refractive index as a p-type nitrogen-based cladding layer while also exhibiting lower resistivity than a p-type nitrogen-based cladding layer.

SUMMARY

According to an embodiment, there is a nitride-based electronic device, which includes an oxide cladding layer, a nitride cladding layer, and a nitride active region layer arranged between the oxide cladding layer and the nitride cladding layer. First and second metal contacts are electrically coupled to the nitride active region layer.

According to another embodiment, there is a method of forming a nitride-based electronic device. A plurality of nitride layers are in a metal organic chemical vapor deposition system. At least a portion of an oxide layer is formed on top of the plurality of nitride layers in the metal organic chemical vapor deposition system.

According to a further embodiment, there is a method of forming an electronic device. A substrate is arranged in a metal organic chemical vapor deposition system. Nitride, metal organic, and n-type vapors are supplied to the metal organic chemical vapor deposition system to successively form a nitride cladding layer and a first nitride waveguide layer. Nitride and metal organic vapors are supplied to the metal organic chemical vapor deposition system to form a nitride active region layer on the first nitride waveguide layer. Nitride, metal organic, and p-type vapors are supplied to the metal organic chemical vapor deposition system to form a second nitride waveguide layer on the nitride active region layer. Nitride, metal organic, and p-type vapors are supplied to the metal organic chemical vapor deposition system to form a nitride contact layer on the second nitride waveguide layer. Oxide and metal organic vapors and one of p-type or n-type vapors are supplied to the metal organic chemical vapor deposition system to form an oxide cladding layer on the nitride contact layer.

According to yet another embodiment, there is a metal organic vapor deposition system, which includes a first reaction chamber comprising a first gas inlet; a second reaction chamber comprising a second gas inlet; and a non-reactive chamber interposed between, and fluidically coupled to, the first and second reaction chambers via first and second valves, respectively.

DETAILED DESCRIPTION

The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to the terminology and structure of nitride-based electronic devices.

Nitride-based electronic devices200A and200B are illustrated inFIGS. 2A and 2B. The nitride-based electronic devices200A or200B include a nitride active region layer225, an oxide cladding layer240(or240A and240B inFIG. 2B), and a nitride cladding layer215. A first waveguide layer220is arranged between the nitride active region layer225and the nitride cladding layer215. A second waveguide layer230is arranged between the nitride active region layer225and the oxide cladding layer240(or240A and240B inFIG. 2B). First205and second245metal contacts are electrically coupled to the nitride active region layer225.

As illustrated inFIGS. 2A and 2B, the nitride-based electronic devices200A and200B also include a nitride-based contact235and a nitride-based substrate210, which can be gallium nitride-based. The nitride cladding layer215can be an aluminum gallium nitride cladding layer, the waveguide layers220and230can be gallium nitride, indium gallium nitride, or aluminum gallium nitride waveguide layers, and the nitride active region layer225can be an indium gallium nitride, gallium nitride, or aluminum gallium nitride multiple-quantum-wells active region. The nitride-based substrate210and the nitride-based layers215-220below the nitride active region layer225are n-type and the nitride-based layers230and235above the nitride active region layer225are p-type.

As will be appreciated by comparingFIG. 1withFIGS. 2A and 2B, the electronic devices200A and200B include an oxide cladding layer240(or240A and240B inFIG. 2B), whereas the electronic device100inFIG. 1has a p-type aluminum gallium nitride cladding layer135. The oxide cladding layer240(or240A and240B inFIG. 2B) can be comprised of n-type indium tin oxide (ITO), n-type zinc oxide (ZnO), or p-type nickel oxide (NiO). The oxide cladding layer240(or240A and240B inFIG. 2B) exhibits improved conductivity compared to the p-type nitride-based cladding layer135in the conventional electronic device ofFIG. 1, while also providing the appropriate refractive index. This refractive index oxide cladding layer240(or240A and240B inFIG. 2B) is appropriate because the refractive indexes n of the cladding layers should satisfy the following relationship—nCladding_Layer<nWaveguide_Layer<nActive_Region_Layer. Because the refractive index of oxides, such as indium tin oxide, zinc oxide, and nickel oxide, is smaller than that of the gallium nitride waveguide layer230, these oxides satisfy the refractive index relationship requirement while also exhibiting improved conductivity compared to an aluminum gallium nitride cladding layer used in conventional devices.

As also will be appreciated by comparingFIG. 1withFIGS. 2A and 2B, the electronic devices200A and200B include the p-type gallium nitride contact235interposed between the p-type gallium nitride waveguide layer230and the oxide cladding layer240(or240A and240B inFIG. 2B), whereas the conventional device100inFIG. 1includes the p-type gallium nitride contact140interposed between the p-type aluminum gallium nitride cladding layer135and the metal contact145. This rearrangement of the location of the p-type gallium nitride contact235is due to the oxide cladding layer employing n-type materials, such as n-type indium tin oxide or n-type zinc oxide.

The oxide cladding layer240of the electronic device200A inFIG. 2Ais formed entirely within a metal organic chemical vapor deposition system, whereas for the electronic device200B, a portion of the oxide cladding layer240A is formed within the metal organic chemical vapor deposition system and the remaining portion of the oxide cladding layer240B is formed outside of the metal organic chemical vapor deposition system, for example, by sputtering or using an electron beam evaporator. Forming at least a portion of the oxide cladding layer240within the metal organic chemical vapor deposition system avoids exposing the device structure to air and prevents any influence of dust, carbon dioxide, and/or oxides in the air. Forming a remaining portion of the oxide cladding layer240outside of the metal organic chemical vapor deposition system reduces the growth time to form the entire oxide cladding layer240.

The nitride-based electronic devices200A and200B illustrated inFIGS. 2A and 2Bcan be lasers. If the nitride-based electronic devices200A and200B are instead light-emitting diodes, then the devices will not include the waveguide layers220and230. In this case, nitride cladding layer215and nitride-based contact235will directly adjoin the nitride active region layer225. It will be recognized that some lasers also do not employ waveguide layers, and thus a laser without waveguide layers220and230can be configured in a similar manner to a light emitting diode.

Methods of forming a nitride-based electronic device having an oxide cladding layer will now be described in connection withFIGS. 2A, 2B, 3, 4, and 5.FIG. 3is schematic diagram of a metal organic chemical vapor deposition system300used for forming a nitride-based electronic device. The system300includes a reaction chamber302into which gasses304are fed. A combination of ammonia (NH3), metal organic (MO), and dopant vapors are fed to form the nitride-based layers and a combination of water (H2O), metal organic, and dopant vapors are fed to form the oxide cladding layer. The reaction chamber is defined by the upper306A and lower306B regions of a quartz tube. A heater308is arranged at the lower region306B of the quartz tube and a substrate210on which the layers are formed is arranged on the heater308. The heater308, which can be a resistive or inductive heater, heats the reaction chamber302while the gasses304are being fed into the tube.

Turning now toFIG. 4, initially a plurality of nitride layers215-235are formed in the metal organic chemical vapor deposition system300(step405). This can be achieved by feeding a combination of ammonia, metal organic, and dopant gases into the reaction chamber302while the heater308heats the chamber302. The type of metal organic gasses will depend upon the layer being formed. Next, at least a portion of an oxide layer240(or240A inFIG. 2B) is formed in the same metal organic chemical vapor deposition system300on top of the plurality of nitride layers215-235(step410). In this regard, note that the nitride and oxide heterostructure may be made by the same MOCVD system without exposing the device parts to the air to prevent influence from dust, CO2, and O2in the air. The combination of nitride MOCVD and oxide MOCVD is unique. The combination of metalorganic (MO) gases and NH3can grow nitrides and the combination of MO and H2O grows oxides in the same MOCVD system. This novel feature is schematically illustrated inFIG. 3. This can be achieved by feeding a combination of water, metal organic, and dopant vapors into the reaction chamber302while the heater308heats the chamber302.

Turning now to the method ofFIG. 5, initially, a substrate210is arranged in the metal organic chemical vapor deposition system (step505). Nitride, metal organic, and n-type dopant vapors304are then supplied to the reaction chamber302to form a nitride cladding layer215on the nitride substrate210(step510). In an embodiment, the nitride cladding layer215is comprised of aluminum gallium nitride, and accordingly the metal organic vapors include aluminum and gallium. Nitride, metal organic, and n-type dopant vapors304are then supplied to the reaction chamber302to form a first nitride waveguide layer220on the nitride cladding layer215(step515). In an embodiment, the first nitride waveguide layer220is comprised of gallium nitride, and accordingly the metal organic vapors include gallium.

Next, nitride and metal organic vapors304are supplied to the reaction chamber302to form a nitride active region layer225on the first nitride waveguide layer220(step520). In an embodiment, the nitride active region layer225is comprised of indium gallium nitride, and accordingly the metal organic vapors include indium and gallium. In another embodiment, the nitride active region layer225is comprised of gallium nitride, and accordingly the metal organic vapors include gallium. The nitride active region layer225is grown in a temperature range of 700-800° C. and the other layers are grown in a temperature range of 900-1050° C. The second nitride waveguide layer230is formed on the nitride active region layer225by supplying nitride, metal organic, and p-type dopant vapors304to the reaction chamber302(step525). In an embodiment, the second nitride waveguide layer230comprises gallium nitride, and accordingly the metal organic vapor includes gallium. The nitride contact layer235is then formed on the second nitride waveguide layer230by suppling nitride, metal organic, and p-type dopant vapors to the reaction chamber302(step530). In an embodiment, the nitride contact layer235comprises gallium nitride, and accordingly the metal organic vapor is gallium.

The oxide cladding layer240is then formed on the nitride contact layer235by supplying oxide, metal organic, and n- or p-type vapors304to the reaction chamber302(step535). In an embodiment, the oxide cladding layer240comprises indium tin oxide, and accordingly the metal organic vapors include indium and tin. In another embodiment, the oxide cladding layer240comprises zinc oxide, and accordingly the metal organic vapors include zinc. In yet another embodiment, the oxide cladding layer240comprises nickel oxide, and accordingly the metal organic vapors include nickel. In the embodiment illustrated inFIG. 2A, the entire oxide cladding layer240is formed in the reaction chamber302, and thus the formed structure is removed from the metal organic chemical vapor deposition system300(step540) and the first205and second245metal contacts are formed (step550). In the embodiment ofFIG. 2B, only the portion240A of the oxide cladding layer is formed in the metal organic chemical vapor deposition system300, and accordingly the formed structure is removed from the metal organic chemical vapor deposition system300(step540), the remainder240B of the oxide cladding layer is formed outside of the metal organic chemical vapor deposition system (step545), and then the first205and second245metal contacts are formed (step550). In an embodiment, the remainder240B of the oxide cladding layer can be formed by sputtering or using an electron beam evaporator. The first205and second245metal contacts can be formed by sputtering or using an electron beam evaporator.

Although embodiments have been described above as using water to form the oxide cladding layer, it will be recognized that any oxidant can be used, including oxygen (O2), alcohols, and other molecules including oxygen atoms.

As noted above, the entire oxide cladding layer is formed within the metal organic vapor deposition system for the device200A illustrated inFIG. 2Aand a portion of the oxide cladding layer is formed within the metal organic vapor deposition system for the device200B illustrated inFIG. 2B. Forming both nitride and oxide layers in a metal organic vapor deposition system is complicated and could result in exposing the device to the ambient environment, which can contain contaminants affecting subsequent layer growth. Specifically, after the nitride layers are formed, the device needs to be removed from the metal organic vapor deposition system and placed into another chemical vapor deposition system (or the same one after clearing the device of all nitride gasses and residues). This removal will expose the device to air, and thus contaminants in the air can land on the top nitride layer, which can affect the quality of the junction with the subsequently formed oxide layer and thus also affect device performance.

A two-reactor metal organic vapor deposition system will now be described in connection withFIG. 6, which addresses problems arising when forming a device that requires growing both nitride and oxide layers. The metal organic vapor deposition system600includes a first reaction chamber605comprising a first gas inlet610and a second reaction chamber615comprising a second gas inlet620. A non-reactive chamber625is interposed between, and fluidically coupled to, the first605and second615reaction chambers via first630A and second630B valves, respectively. The first630A and second630B valves can be, for example, gate valves.

As illustrated, the inlet610of the first reaction chamber605is configured to receive gasses, which in the illustrated embodiment are nitride (NH3) and metal organic (MO) gasses, and thus this chamber can be referred to as a nitride reaction chamber. Similarly, the inlet620of the second reaction chamber615is configured to receive gasses, which in the illustrated embodiment include an oxidant and metal organic (MO) gasses, and thus this chamber can be referred to as an oxide reaction chamber. The oxidant can be, for example, water (H2O), oxygen (O2), alcohols, and other molecules that include oxygen atoms. Although this discussion refers to the first reaction chamber605as a nitride reaction chamber and the second reaction chamber615as an oxide reaction chamber, the first reaction chamber605can be an oxide reaction chamber (assuming it is fed with oxide gas) and the second reaction chamber can be a nitride reaction chamber (assuming it is fed with nitride gas).

Although not illustrated for purposes of clarity, it will be recognized that the first605and second615reaction chambers will each include a heater, as well as a mechanism for activating the heater, which can be a resistive or inductive heater.

The operation of the two-reactor metal organic vapor deposition system600will now be described in connection with the formation of the device200A illustrated inFIG. 2A. The substrate210is initially placed in either of the first reaction chamber605or the non-reactive chamber625. If the substrate210is initially placed in the non-reactive chamber625, that chamber is evacuated so as to remove any contaminants while valves630A and630B are closed and then valve630A is opened and the substrate210is moved into the first reaction chamber605. The substrate210can be moved between the non-reactive chamber625and the first605and second615reaction chambers using a robotic arm or by human hands using a glove box. In the embodiment illustrated inFIG. 6, a robotic arm635, under the control of a controller640, moves the substrate210between the non-reactive chamber625and the first605and second615reaction chambers. The controller640can be any type of controller configured to control the operation and movement of robotic arm635, including a microprocessor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), etc. If the controller is a microprocessor, the microprocessor controls the operation and movement of robotic arm635using instructions loaded from a memory (not illustrated).

The nitride layers215-235are then formed in the first reaction chamber605by feeding nitride and metal organic gasses into the first reaction chamber605via the first inlet610while the substrate210is heated. The first reaction chamber605is then evacuated to remove any residual nitride gasses and then the first valve630A is opened so that the substrate210carrying layers215-235can be moved into the non-reactive chamber625. The first valve630A is then closed and the second valve630B is then opened to transfer the substrate210carrying layers215-235into the second reaction chamber615. The second valve630B is then closed and the oxide cladding layer240is then formed in the second reaction chamber615by feeding oxide and metal organic gasses into the second reaction chamber605via the second inlet620while the substrate210is heated.

Thus, the two-reactor metal organic vapor deposition system600allows the growth of both oxide and nitride layers for a single device without exposing the layers to contaminants in the ambient environment between the growth of different layers, and thus does not suffer from reduced device performance that can arise when the layers are exposed to air between layer growth.

It should be recognized that the two-reactor metal organic vapor deposition system600can be operated in a similar manner to form the device200B illustrated inFIG. 2B. Further, although these examples involve first forming nitride layers and then forming an oxide layer, the two-reactor metal organic vapor deposition system600can be operated to first form one or more oxide layers and then form one or more nitride layers. Moreover, the two-reactor metal organic vapor deposition system600does not need to form all of the nitride or oxide layers first and then forming the other of the nitride or oxide layers. Specifically, the formation of the nitride and oxide layers can be performed repeatedly, such as, for example, forming one or more nitride layers, followed by one or more oxide layers, followed by forming one or more nitride layers, etc.

The oxide cladding layer in the disclosed nitride-based electronic devices exhibits better conductivity than conventional nitride-based electronic devices with two nitride-based cladding layers while still providing an appropriate refractive index to confine light in the waveguide layers. The better conductivity provides a more energy efficient device, which also increases the overall useful life of the device.

The disclosed embodiments provide a nitride-based electronic device and method of forming such a device. It should be understood that this description is not intended to limit the invention. On the contrary, the exemplary embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the exemplary embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.