Impact of Ga/N flux ratio on trap states in n-GaN grown by plasma-assisted molecular-beam epitaxy

Abstract

Deep level transient spectroscopy in plasma-assisted molecular beam epitaxy grown Al 0.2 Ga 0.8 N / GaN interface and the rapid thermal annealing effect Appl. Phys. Lett. 97, 112110 (2010); 10.1063/1.3491798Effect of N to Ga flux ratio on the GaN surface morphologies grown at high temperature by plasma-assisted molecular-beam epitaxyThe effect of growth regime on the deep level spectrum of n-GaN using molecular-beam epitaxy ͑MBE͒ was investigated. As the Ga/N flux ratio was decreased towards Ga-lean conditions, the concentration of two acceptor-like levels, at E c Ϫ3.04 and 3.28 eV, increased from 10 15 to 10 16 cm Ϫ3 causing carrier compensation in these films. Thus, these two traps behaved as the dominant compensating centers in MBE n-GaN. Furthermore, the increase in trap concentration also strongly correlated with the degradation of both surface morphology and bulk electron mobility towards Ga-lean conditions, where higher pit densities and lower mobility were observed. These results show that the growth regime directly impacts all morphology, bulk transport, and trap states in n-GaN.

Comparison of deep level incorporation in ammonia and rf‐plasma assisted molecular beam epitaxy n‐GaN films

“…16 cm -3 , to support DLOS and DLTS experiments, following our previously reported growth conditions [2]. The ammonia samples were grown at a substrate temperature of 770 °C using two different nominal V/III ratios of 750 and 1500, which were achieved by varying the ammonia flux during growth.…”

A novel method to investigate defect states in MBE grown highly resistive GaN doped with C and Si

“…Positive onsets correspond to deep acceptors, confirmed by DLOS analysis accounting for the photon flux of the monochromatized light, at E C -E t = 1.35, 2.40 and 3.28 eV for the NC sample and at E C -E t = 1.35, 1.94, 2.54 and 3.28 eV for the C-doped samples. The E C -2.40 eV deep level has been previously associated with V Ga in n-type MBE GaN without intentional C doping [7]. The E C -1.35 eV state has been attributed to C [3,7], while the E C -1.94 eV level is reported here for the first time and appears to be particular to MBE-grown GaN:C. The E C -3.28 eV level has been attributed to the C N acceptor in experimental studies [3 ,7], and its position in the bandgap agrees well with theoretical predictions for C N [4].…”

“…The E C -2.40 eV deep level has been previously associated with V Ga in n-type MBE GaN without intentional C doping [7]. The E C -1.35 eV state has been attributed to C [3,7], while the E C -1.94 eV level is reported here for the first time and appears to be particular to MBE-grown GaN:C. The E C -3.28 eV level has been attributed to the C N acceptor in experimental studies [3 ,7], and its position in the bandgap agrees well with theoretical predictions for C N [4]. The E C -2.54 eV level emerges with C doping, suggesting a relation to C impurities.…”

Influence of Ga/N ratio on morphology, vacancies, and electrical transport in GaN grown by molecular beam epitaxy at high temperature

“…6͔͒ were much higher in N-rich as in Ga-rich grown films. [7][8][9] These V Ga -O N complexes are acceptor states in unintentionally doped ͑UID͒ n-type GaN and cause electrical compensation. 6,[10][11][12] Optimized films by Ga-rich/low-T PAMBE growth have, however, suffered from extreme growth control at the boundary for Ga droplet formation, and second, relatively large reverse-bias leakage currents through charged threading dislocations ͑TDs͒.…”