Structural, electrical, and optical properties of defects in Si-doped GaN grown by molecular-beam epitaxy on hydride vapor phase epitaxy GaN on sapphire

Abstract

Molecular-beam epitaxy (MBE) has been utilized to grow Si-doped GaN layers on GaN/sapphire templates prepared by hydride vapor phase epitaxy. An extensive set of characterization techniques is applied to investigate the layers. Positron annihilation experiments indicate that the samples contain open volume defects, most likely clusters of vacancies and possibly Ga vacancy-donor complexes. The number of vacancy clusters decreases, as Si concentration is increased. Photoluminescence spectra show that while the absolute intensity of both the yellow and ultraviolet (UV) band-edge transitions increase with Si doping, the intensity ratio of yellow-to-UV emission is decreased. Secondary ion mass spectrometry indicates that the impurity concentrations are in qualitative agreement with the carrier concentrations determined in electrical experiments. The data suggest further that silicon does not affect the diffusion of oxygen. Moreover, transmission electron microscopy reveals that MBE-grown GaN retains the threading dislocation structure of the GaN/sapphire substrate. The MBE layer is also shown to grow in the Ga face orientation, but some inversion boundaries are present in the epilayer.

Characterization of mass-transport grown GaN by hydride vapour-phase epitaxy

“…The (S, W) points fall clearly off the line characteristic of the Ga vacancy (V Ga -O N complex) identified earlier [18,19]. On the other hand, the data fits well with the line previously associated to vacancy clusters formed in MBE grown GaN samples [20,21]. Instead of simple point defects like V Ga and V Ga -O N , the MT region thus contains empty vacancy clusters where several Ga and N atoms are missing.…”

“…In addition, we recorded RS spectra (not shown here) taken in several spots circularly arranged around a barrier stripe in order to check for in-plane distribution of the strain in the MT areas. No shift of the E 2 mode [20,21]) are also shown. was observed, showing a homogeneous strain distribution.…”

The influence of AlN buffer layer thickness on the properties of GaN epilayer

“…The ratio is minimum when buffer layer thickness are 30 and 20 nm for samples grown on SP substrate and DP substrate, respectively. Generally it is thought that the YL relates to point defects, such as V Ga ; V Ga -related compounds and other impurities [25,26]. Theoretical calculation indicated that dislocations in GaN acted as acceptors and perhaps related to the source of YL [27,28].…”

Positron annihilation in (Ga, Mn)N: A study of vacancy-type defects

“…For all the samples, the S parameters first decrease rapidly at low energy, which results from positron annihilations and formation of positronium atoms at sample surface. 15 As the positron implantation energy increased, fewer positrons are able to diffuse to the sample surface. At 3 -20 keV the S parameter becomes approximately constant indicating almost all positrons are annihilated in the bulk layer.…”