Intrinsic compensation of silicon-doped AlGaN

Abstract

The silicon doping characteristics of AlxGa1−xN were investigated over the x=0.2–0.5 composition range. A combination of Hall and capacitance–voltage measurements indicated a significant deepening of the Si level, as well as a systematic increase in carrier compensation with increasing compositions. Optical isothermal capacitance transient spectroscopy also revealed the presence of two midgap states with concentrations in the low 1017 cm−3 range. The two levels, which are thought to be responsible for the observed compensation, have been assigned to the third and second ionization states of the aluminum vacancy.

Influence of silicon doping on vacancies and optical properties of AlxGa1−xN thin films

“…Wagener et al reported on the deepening of the Si level with increasing Al content ͑x = 0.2-0.5͒, as well as on the presence of two levels in the band gap thought to be responsible for the compensation. 8 Keller et al proposed that observed PL transition in the 510-550 nm range is due to the group-III vacancy. 9 In this letter, we confirm the correlation between the vacancy concentration in the group-III sublattice and the photoluminescence ͑PL͒ transition in the 510-550 nm range by combining positron annihilation spectroscopy ͑PAS͒ with photoluminescence measurements.…”

Investigating the electrical properties of Si donors in AlxGa1–xN alloys

“…[7]). Both the mobility and carrier concentration decreased sharply with increasing Al, with Al x Ga 1-x N of x ≥ 0.5 being very resistive.…”

“…This shows that Si remains a shallow donor in Al x Ga 1-x N, at least up to x = 0.65. With this in mind, it is thought that the low free carrier concentration measured for the moderately doped Al 0.51 Ga 0.49 N, as well as for the Al 0.65 Ga 0.35 N sample, is most likely due to self compensation by Al vacancies, which has been shown to be a triple acceptor in Al x Ga 1-x N [7].…”

The effect of Si‐doping on the variable temperature photoluminescence properties of AlGaN alloys

“…This would also explain the increase in the E loc energy observed in Si-doped material. The nature of the second non-radiative channel with acti-* The carrier concentration was determined from capacitance-voltage measurements [3]. No Hall measurements could be performed on this sample due to a large density of cracks.…”

“…The photoluminescence measurements were performed between 12 and 300 K, using a 20 mW frequency doubled argon ion laser (λ = 244 nm). The electrical properties of the layers were investigated using Hall effect measurements, the results of which are published elsewhere [3,4]. Undoped Al x Ga 1-x N: For the undoped GaN sample ( Fig.…”