Hybrid growth method for iii-nitride tunnel junction devices

Abstract

A hybrid growth method for III-nitride tunnel junction devices uses metal-organic chemical vapor deposition (MOCVD) to grow one or more light-emitting or light-absorbing structures and ammonia-assisted or plasma-assisted molecular beam epitaxy (MBE) to grow one or more tunnel junctions. Unlike p-type gallium nitride (p-GaN) grown by MOCVD, p-GaN grown by MBE is conductive as grown, which allows for its use in a tunnel junction. Moreover, the doping limits of MBE materials are higher than MOCVD materials. The tunnel junctions can be used to incorporate multiple active regions into a single device. In addition, n-type GaN (n-GaN) can be used as a current spreading layer on both sides of the device, eliminating the need for a transparent conductive oxide (TCO) layer or a silver (Au) mirror.

1 . A method for fabricating a III-nitride based semiconductor device, comprising:
 performing a first growth of a p-n junction with III-nitride based p-type material using metal-organic chemical vapor deposition (MOCVD); and   performing a subsequent regrowth of III-nitride based n-type material using a different growth technique than MOCVD.   
     
     
         2 . A III-nitride based semiconductor device, comprising:
 one or more light-emitting or light-absorbing structures grown by metal-organic chemical vapor deposition (MOCVD), wherein the light-emitting or light-absorbing structures include one or more p-type III-nitride layers; and   one or more tunnel junctions grown by ammonia-assisted or plasma-assisted molecular beam epitaxy (MBE) on the light-emitting or light-absorbing structures, wherein the tunnel junctions include one or more n-type III-nitride layers that are grown on the p-type III-nitride layers of the light-emitting or light-absorbing structures, and a regrowth interface between the p-type III-nitride layers and the n-type III-nitride layers serves as a p-n interface in the tunnel junction.   
     
     
         3 . A III-nitride based semiconductor device, comprising:
 a first growth of a III-nitride based p-n junction structure comprised of III-nitride based p-type material and III-nitride based n-type material, wherein the III-nitride based p-type material is grown using metal-organic chemical vapor deposition (MOCVD); and   a subsequent regrowth of the III-nitride based p-n junction structure, wherein the III-nitride based n-type material is regrown on the III-nitride based p-type material using a different growth technique than MOCVD, and a tunnel junction is formed at an interface between the III-nitride based p-type material and the III-nitride based n-type material.   
     
     
         4 . The device of  claim 3 , where the subsequent regrowth is performed under conditions that prevent passivation of the III-nitride based p-type material. 
     
     
         5 . The device of  claim 3 , wherein the subsequent regrowth of the III-nitride based p-type material is highly doped to reduce contact resistance. 
     
     
         6 . The device of  claim 3 , wherein the subsequent regrowth ends with the III-nitride based n-type material, allowing for buried activated III-nitride based p-type layers to be grown. 
     
     
         7 . The device of  claim 3 , wherein delta-doping is used at the regrowth interface. 
     
     
         8 . The device of  claim 3 , further comprising a regrown active region grown on or above the subsequent regrowth using MOCVD. 
     
     
         9 . The device of  claim 8 , wherein the first growth is a light-emitting diode (LED) and the regrown active region is a second LED of similar emission wavelength, such that efficiency droop is reduced through use of multiple active regions. 
     
     
         10 . The device of  claim 8 , wherein layers grown by performing another growth are of similar wavelengths and are aligned to peaks of a cavity mode in a vertical-cavity surface-emitting laser (VCSEL), such that each active region has large enhancement factors. 
     
     
         11 . The device of  claim 8 , wherein the first growth is a III-nitride optoelectronic device, and the regrown active region is a longer wavelength single or multiple quantum well structure that is optically pumped by emission of shorter wavelength from the first growth. 
     
     
         12 . The device of  claim 11 , wherein the longer wavelength single or multiple quantum well structure is a photodiode used to monitor the emission of shorter wavelength from the first growth or regrown active region. 
     
     
         13 . The device of  claim 8 , wherein the regrown active region is a III-nitride optoelectronic device, and the first growth is a longer wavelength single or multiple quantum well structure that is optically pumped by emission of shorter wavelength from the regrown active region. 
     
     
         14 . The device of  claim 13 , wherein the longer wavelength single or multiple quantum well structure is a photodiode used to monitor the emission of shorter wavelength from the first growth or regrown active region. 
     
     
         15 . The device of  claim 8 , wherein the first growth is a light-emitting diode (LED), and the regrown active region is an LED of a different emission wavelength. 
     
     
         16 . The device of  claim 3 , wherein the device is a III-nitride optoelectronic device and a top n-type layer of the tunnel junction serves as a current spreading layer. 
     
     
         17 . The device of  claim 3 , wherein the device is a III-nitride optoelectronic device, and the tunnel junction is used to screen or enhance polarization fields in active regions. 
     
     
         18 . The device of  claim 3 , wherein the device is a III-nitride optoelectronic device, and the tunnel junction allows for use of a thin p-type material to reduce electrical and optical losses in the III-nitride based p-type material. 
     
     
         19 . The device of  claim 3 , wherein the device is a light-emitting diode (LED), and sheet resistance on both sides of the III-nitride based p-n junction structure is matched to reduce current crowding. 
     
     
         20 . The device of  claim 3 , wherein the device is a light-emitting diode (LED), and top and bottom III-nitride layers of the LED are roughened to increase an extraction efficiency of the LED. 
     
     
         21 . The device of  claim 3 , wherein the device is a vertical cavity surface-emitting laser (VCSEL) processed in a flip-chip geometry with one or more high reflectivity optical coatings to enhance light extraction or confine an optical mode in the VCSEL. 
     
     
         22 . The device of  claim 3 , wherein the device is a multi junction solar cell or photodiode. 
     
     
         23 . The device of  claim 3 , wherein a single metal contact deposition is used to fabricate contacts to III-nitride based n-type layers of the device. 
     
     
         24 . The device of  claim 3 , wherein the subsequent regrowth is performed using ammonia-assisted or plasma-assisted molecular beam epitaxy (MBE). 
     
     
         25 . The device of  claim 3 , wherein a top III-nitride layer of the tunnel junction eliminates the need for a p-contact grid. 
     
     
         26 . The device of  claim 3 , wherein each buried III-nitride layer is contacted, such that current flowing through each active region is controlled individually.