Doping of MBE grown cubic GaN on 3C-SiC (001) by CBr[sub 4]

Abstract

We report on carbon doping of cubic GaN by CBr 4 using plasma-assisted molecular beam epitaxy on 3C-SiC (001) substrates. The samples consist of a 70 nm thick GaN buffer followed by a 550 nm thick GaN:C layer. Carbon doping is realized with a home-made carbon tetrabromide sublimation source. The CBr 4 beam equivalent pressure was established by a needle valve and was varied between 2x10 -9 mbar and 6x10 -6 mbar. The growth was controlled by in-situ reflection high energy electron diffraction. The incorporated carbon concentration is obtained from secondary ion mass spectroscopy. Capacitance voltage characteristics were measured using metal-insulator-semiconductor structures. Capacitance voltage measurements on nominally undoped cubic GaN showed n-type conductivity with N D -N A =1x10 17 cm -3 . With increasing CBr 4 flux the conductivity type changes to p-type and for the highest CBr 4 flux N A -N D =4.5x10 18 cm -3 was obtained.

Carbon as an acceptor in cubic GaN/3C–SiC

“…(1.1), SIMS measurements revealed that the density of incorporated carbon is at least one order of magnitude higher than the net donor/ acceptor density N CV . We assume that about 10% of the incorporated carbon act as acceptors whereas about 90% form selfcompensated defects as discussed in [3] in detail. Fig.…”

“…Due to the high conductivity of the 3C-SiC substrates the doping concentration of our samples cannot be obtained by the Hall effect measurements. Thus, the net donor N D ÀN A and acceptor N A À N D concentrations were calculated using capacitance-voltage (CV) data [3]. CV measurements were performed on metal-insulator-semiconductor (MIS) structures at 1 MHz and 50 mV AC level by an Agilent Precision LCR Meter E4980A.…”

Cubic zincblende gallium nitride for green-wavelength light-emitting diodes

“…Owing to the difficulties with magnesium p-type doping, a few studies have investigated p-type doping of zincblende GaN by carbon [70][71][72]. Carbon is a group IV element, which can either replace the group V nitrogen site as an acceptor or the group III gallium site as a donor, resulting in potential amphoteric behaviour.…”

“…Carbon doping has been achieved through electron beam evaporation of a graphite rod [70] and sublimation of solid CBr 4 powder [71,72]. The maximum carbon incorporation concentrations were 2 × 10 20 cm −3 from As et al [70] and 1 × 10 20 cm −3 from Zado et al [72] before the zincblende GaN film degraded in quality.…”