Optimization of Growth and Activation of Highly Doped p-type GaN for Tunnel Junctions

Abstract

ABSTRACTHighly doped p-type GaN was grown by MOCVD with a Mg source for use in tunnel junctions for dual wavelength light emitting diodes. Highly doped p-type material (p+) is necessary for creating efficient tunnel junctions that act as buried current spreading layers and provide high quality contacts to p-type GaN. Molar flow ratios and growth temperature were varied to achieve maximum doping concentration. A range of post-growth annealing conditions to activate incorporated Mg was investigated. Secondary Ion Mass Spectrometry (SIMS) and Hall effect were used to measure Mg incorporation and carrier concentration, respectively. The maximum carrier concentration achieved employed a hybrid growth scheme that achieved high carrier concentration and high quality material by alternating layers of high and low growth temperature material. Atmospheric annealing was compared to standard RTA under N2 ambient. Successful GaN tunnel junctions were grown using the hybrid p-type doping scheme developed in this work. I-V measurements were taken on these devices to evaluate the effectiveness of the devices.