Microwave annealing of Mg-implanted and in situ Be-doped GaN

Abstract

An ultrafast microwave annealing method, different from conventional thermal annealing, is used to activate Mg-implants in GaN layer. The x-ray diffraction measurements indicated complete disappearance of the defect sublattice peak, introduced by the implantation process for single-energy Mg-implantation, when the annealing was performed at Ն1400°C for 15 s. An increase in the intensity of Mg-acceptor related luminescence peak ͑at 3.26 eV͒ in the photoluminescence spectra confirms the Mg-acceptor activation in single-energy Mg-implanted GaN. In case of multiple-energy implantation, the implant generated defects persisted even after 1500°C / 15 s annealing, resulting in no net Mg-acceptor activation of the Mg-implant. The Mg-implant is relatively thermally stable and the sample surface roughness is 6 nm after 1500°C / 15 s annealing, using a 600 nm thick AlN cap. In situ Be-doped GaN films, after 1300°C / 5 s annealing have shown Be out-diffusion into the AlN layer and also in-diffusion toward the GaN/SiC interface. The in-diffusion and out-diffusion of the Be increased with increasing annealing temperature. In fact, after 1500°C / 5 s annealing, only a small fraction of in situ doped Be remained in the GaN layer, revealing the inadequateness of using Be-implantation for forming p-type doped layers in the GaN.

Ultra-Fast Microwave Heating for Large Bandgap Semiconductor Processing

“…The fast out-diffusion and in-diffusion of Mg in GaN at high annealing temperatures is due to a high diffusion coefficient of acceptors in III-V compounds. The extracted Mg implant doses in microwave annealed GaN samples are slightly lower compared to the extracted dose in the as-implanted GaN material due to out-diffusion of Mg into the deposited AlN cap during microwave annealing (Aluri et al, 2010). Despite of the out-and in-diffusion of the Mg implant during annealing, the implant profiles are reasonably stable at least up to a microwave annealing temperature of 1400 ºC.…”

“…The MgO capping layer (200 nm thick), formed by e-beam evaporation, and having 6.5% lattice mismatch with GaN, could protect GaN only up to a microwave annealing temperature of 1300 ºC (Sundaresan et al, 2007d). Pulsed-laser-deposited AlN(600 nm thick), having a 2.6% lattice mismatch with GaN, protects GaN layers reasonably well up to microwave annealing temperatures as high as 1500 ºC (Sundaresan et al, 20007;Aluri et al, 2010). Surface roughness of AlN capped GaN is comparable to that of a virgin sample for 5s annealing but increases with increasing annealing time at 1500 ºC (see Fig.…”

“…High-temperature microwave annealing of GaN results in a very rough (≥ 10nm) surface with formation of hexagonal cavities, due to sublimation (Aluri et al, 2010;Sundaresan et al, 2007d). It is well known that nitrogen sublimates from GaN even at annealing temperatures as low as 700 ºC, but temperatures as high as 1500 ºC are required for activating ion-implanted Mg acceptors in GaN.…”

“…Tian & M.Y. Tian, 2009;Aluri et al, 2010). In this novel annealing method, microwaves coming from a microwave head are coupled to the sample directly.…”

Caracterização estrutural e magnética de amostras de c-GaN implantadas com Fe, Mn e Cu

“…De uma maneira geral a temperatura necessária para um tratamento térmico efetivoé de dois terços do ponto de fusão do material [26] o que para o GaN significaria uma temperatura de tratamento em torno de 1800 • C. Estudos em h-GaN mostram que a recuperação da rede nãoé completa mesmo em temperaturas de até 1500 • C [27]. Entretanto, em temperaturas a partir de 720 • C o material se decompõe termicamente com liberação de gás nitrogênio o que torna proibitivo o tratamento em condições ideais.…”