The origins and properties of intrinsic nonradiative recombination centers in wide bandgap GaN and AlGaN

Abstract

Large electron capture-cross-section of the major nonradiative recombination centers in Mg-doped GaN epilayers grown on a GaN substrateThe nonradiative lifetime (s NR ) of the near-band-edge emission in various quality GaN samples is compared with the results of positron annihilation measurement, in order to identify the origin and to determine the capture-cross-section of the major intrinsic nonradiative recombination centers (NRCs). The room-temperature s NR of various n-type GaN samples increased with decreasing the concentration of divacancies composed of a Ga vacancy (V Ga ) and a N vacancy (V N ), namely, V Ga V N . The s NR value also increased with increasing the diffusion length of positrons, which is almost proportional to the inverse third root of the gross concentration of all point defects. The results indicate that major intrinsic NRC in n-type GaN is V Ga V N . From the relationship between its concentration and s NR , its hole capture-cross-section is estimated to be about 7 Â 10 À14 cm 2 . Different from the case of 4H-SiC, the major NRCs in p-type and n-type GaN are different: the major NRCs in Mg-doped p-type GaN epilayers are assigned to multiple vacancies containing a V Ga and two (or three) V N s, namely, V Ga (V N ) n (n ¼ 2 or 3). The ion-implanted Mgdoped GaN films are found to contain larger size vacancy complexes such as (V Ga ) 3 (V N ) 3 . In analogy with GaN, major NRCs in Al 0.6 Ga 0.4 N alloys are assigned to vacancy complexes containing an Al vacancy or a V Ga . Published by AIP Publishing. https://doi.

High‐Temperature Annealing of AlGaN

“…Furthermore, it should be noted that HTA could also lead to absorption by formation of group‐III and N vacancies, which are suspected of being able to cluster and form nonradiative recombination centers. [ 26 ] The aim of further process optimization must in any case be to avoid UV absorption and hence to avoid the formation of intrinsic defects during AlGaN annealing.…”

Structural and optical impacts of AlGaN undershells on coaxial GaInN/GaN multiple-quantum-shells nanowires

“…In addition, A. Armstrong et al have identified surface deep-level defects and an effective passivation mechanism of an AlGaN shell on GaN NWs [29]. Fundamentally, the AlGaN shell is likely to reduce the point defects on the surface of GaN core NWs due to lower surface mobility of Al, as well as a lower formation energy of vacancies in the AlGaN layer than that in GaN core NWs [30][31][32][33]. For this reason, it is necessary to conduct a detailed investigation to gain insight into the trapping effect of point defects by the AlGaN undershell in terms of its structural and optical impacts on coaxial GaInN/GaN MQS NWs.…”

Interfacial N Vacancies in GaN /( Al<

“…The backdiffusion of positrons in the doped samples induces much more gradual reduction of the S parameter. Typically, a higher S parameter indicates more positrons getting trapped at vacancy defects such as the Ga vacancy V Ga in GaN [32][33][34], or positrons getting trapped at bigger vacancy defects. However, the increase in the S parameter is in this case associated with the increase of the effective positron diffusion length.…”