A pathway to controllable n-type doping in AlGaN alloys for high power devices

North Carolina State University, Raleigh NC

Investigators

Abstract

Abstract: Control of the electrical conductivity of the wide bandgap alloy AlGaN for high power applications The proposed research will extend the applicability of wide bandgap semiconductors beyond the traditional limits by novel doping and defect control processes. This will lead to effective control of electrical conductivity
in materials that were traditionally classified as insulators. Extending the current limits of doping extends the functionality of this class of materials to realize applications that otherwise would not be possible.. This research will provide for a transformative and disruptive technology for power electronics and also provide a breakthrough technology for efficient doping to realize efficient deep UV emitters for water purification. The successful demonstration of such disruptive technology would revolutionize energy switching and transmission, energy storage, and related applications in electrical motor drives and other power intensive applications within the US. As such, the White House has recognized the need to build America?s leadership in this technology as part of the manufacturing innovation institutes. In general, this research will directly lead to materials that will be used for applications that deal with the preservation and extension of natural resources by: (1) allowing for the efficient
use and transmission of electrical energy, (2) availability of clean potable water through
disinfection by the use of UV, and (3) the detection of pollutants and other effluents. This
program will provide the opportunity to educate a Ph.D. student with support from an undergraduate student on the growth and characterization of wide bandgap materials while participating with the group?s international collaborators network. The ultimate technical goal of this proposal is to demonstrate controllable n-doping in AlGaN over the whole compositional range and to demonstrate an AlGaN-based power Schottky diode that will exceed the performance of competing SiC-based devices. The following challenges need to be met: (1) establishment of dopant incorporation and solubility limits as well as activation energies for Si and Ge;
(2) identification of compensating defects and impurities in AlGaN:Si/Ge; (3) control of the identified compensators using a supersaturation and a novel Fermi level point defect control scheme; (4) demonstration of controllable low, intermediate, and high free electron densities in AlGaN; (5) fabrication of a power Schottky diode. These challenges can be finally met based on recent advanced in AlGaN thin film growth on native substrates as well as recent results on Ge-doping of GaN. The WideBandgap Laboratory at NCSU has been in the forefront of these developments by demonstrating not only the point defect control schemes but also by demonstrating its capabilities such as the first demonstration
of a deep-UV laser with observable cavity modes. All these achievements have been realized using the state-of-the-art metalorganic chemical vapor deposition facility at NCSU. Identification of compensating defects and impurities will
lead to better understanding of defect complexes in AlGaN and defect formation in wide bandgap materials. Since the proposed Fermi level control scheme is independent of III-nitrides, 
the demonstration of advanced point level control will promote its application in other material systems.