High carrier concentrations of n- and p-doped GaN on Si(111) by nitrogen plasma-assisted molecular-beam epitaxy

Abstract

High-quality doped GaN layers were grown on silicon substrates by radio frequency nitrogen plasma-assisted molecular-beam epitaxy. High-temperature-grown AlN (about 200 nm) was used as a buffer layer. In-growth doping was done using high-purity Si and Mg as n- and p-type dopants, respectively. X-ray diffraction revealed that monocrystalline GaN was obtained. This is in good agreement with the results of morphological study by atomic force microscopy. Micro-photoluminescence (PL) and micro-Raman spectroscopy were used to study the room-temperature optical properties of the doping films. No yellow-band emission was observed in the PL spectroscopy. From the Hall measurements, the resulting n-type doping concentration was measured to be (1–2) × 1019 cm−3. Fairly uniform hole concentration as high as (4–5) × 1020 cm−3 throughout the GaN crystal was achieved. In terms of the carrier concentration, it was found that the results determined from the Fourier transform infrared analysis are in good agreement with the results determined from the Hall measurements.