Arsenic-doped p-type ZnO (p-ZnO:As) thin films were deposited by the magnetron sputtering technique. High-resolution low-temperature photoluminescence (PL) spectra of the films revealed emissions at 3.35 eV and 3.32 eV, representing the neutral-acceptor-bound exciton transition and the free electron to acceptor level transition. Electroluminescence spectra of the p-n diodes fabricated from the p-ZnO:As/n-GaN heterostructure showed UV emission at about 380 nm and yellowish visible lights centered at 600-650 nm, which resembled the PL spectrum of the ZnO:As layer. The p-type ZnO films with 1at% As grown at 500 • C showed a hole concentration of 5 × 10 12 -7 × 10 13 cm −3 after the deposition and 4 × 10 14 -1 × 10 16 cm −3 after annealing at 600 • C in oxygen atmosphere. High-resolution x-ray photoelectron spectroscopy indicated that most of the As dopants occupy Zn sites within the ZnO:As films.

The inductively coupled plasma-reactive ion etching (ICP-RIE) of SiC single crystals using the C 2 F 6 /O 2 gas mixture was investigated. It was observed that the etch rate increased as the ICP power and bias power increased. With increasing sample-coil distance, O 2 concentration, and chamber pressure, the etch rate initially increased, reached a maximum, and then decreased. Mesas with smooth surfaces (roughness Յ 1 nm) and vertical sidewalls (ϳ85°) were obtained at low bias conditions with a reasonable etch rate of about 100 nm/min. A maximum etch rate of 300 nm/min could be obtained by etching at high bias conditions (Ն300 V), in which case rough surfaces and the trenched sidewall base were observed. The trenching effect could be suppressed by etching the samples on anodized Al plates, although mesas with sloped (60-70°) sidewalls were obtained. Results of various surface characterization indicated little contamination and damage on the etched SiC surfaces. 210Kong, Choi, Lee, Han, and Lee Fig. 1. Etch characteristics of 6H-SiC and 4H-SiC as a function of (a) ICP source power, (b) bias power, (c) pressure, (d) O 2 percentage in C 2 F 6 /O 2 , and (e) the distance between the substrate holder and the source coil.

No abstract