p-Type GaN Obtained by Electron Beam Irradiation

Abstract

In order to use GaN for blue light emitting diodes (LEDs) and laser diodes (LDs) the long standing problem of high p-type doping had to be solved. Amano et al. [157, 158] grew Mg-doped GaN films using AlN buffer layers on a sapphire substrate. After growth, low-energy electron beam irradiation (LEEBI) treatment was performed on these GaN films and p-type GaN films were obtained. The hole concentration was 10¹⁷ cm^-3 and the lowest resistivity was 12 Ωcm. These values were not sufficient for the fabrication of blue LDs and high-power blue LEDs. It has been explained in Sects. 4.5 and 4.6 that GaN films grown with GaN buffer layers are superior in terms of their electrical characteristics [159] to those with A1N buffer layers. In the present section the characteristics of p-type Mg-doped GaN films grown with GaN buffer layers on sapphire substrates are described.