Depth profiling measurements of photoluminescence on GaN epitaxial films grown on c-plane sapphire with metalorganic chemical vapor deposition have been performed. Dry etching technique of reactive ion etching is used with reactive gas of CCl2F2/H2/Ar under an operation power of 200 W. Before and after each etching, reflectivity and photoluminescence spectra are measured. Film thickness is determined from both the scanning electron microscopy and the interference oscillations of the reflectivity spectra. An excellent steady etching rate of 19.2 nm/min is established. The photoluminescence measurements show that both the near-band-edge and the yellow luminescence remain fairly constant until the film thickness of about 700 nm, and a large drop is obtained in the ratio of near-band-edge to yellow emission intensity under about 300 nm. Analysis shows that the yellow luminescence emitters are mostly confined within the near interface region, and supports the origin of yellow luminescence to be due to native defects instead of impurities.

͑Received 29 December 1997͒Near-band-gap UV and yellow band emission from metal-organic chemical vapor deposition grown GaN films on sapphires are investigated under laser excitation. The intensities of the UV and the yellow peaks increase at different rates as the entrance slit width of the spectrometer increases. The spatial distribution of the luminescence emission is analyzed through the dependence of photoluminescence intensity on the slit widths of the spectrometer. The yellow emission originates from a spot with a size about 1.5 times larger in diameter than the UV emission. Using an absorption mechanism, a Lorentzian line-shape distribution fit with the data gives estimated effective absorption coefficients of 47 cm Ϫ1 for the UV signal at 364 nm and of 32 cm Ϫ1 for the yellow signal at 546 nm, which agrees perfectly with the ones from an exponential decay fit. Dependence of UV-to-yellow peak ratio on the slit widths of the spectrometer, and consistence with possible origins of yellow luminescence is discussed. ͓S0163-1829͑98͒03132-4͔

Articles you may be interested in dc and rf characteristics of self-aligned inversion-channel In 0.53 Ga 0.47 As metal-oxide-semiconductor fieldeffect transistors using molecular beam epitaxy-Al 2 O 3 / Ga 2 O 3 ( Gd 2 O 3 ) as gate dielectrics Photoluminescence and photoreflectance study of InGaAs/AlAsSb quantum wells grown by molecular-beam epitaxy Device-quality Ga 2 O 3 ͑Gd 2 O 3 ͒ thin films have been grown on GaAs using molecular-beam epitaxy. Photoluminescence measurements have been performed within a temperature range of 4.2-300 K. Detailed analysis on the peak position, peak width, and peak intensity has been compared with those of a conventional Al 0.45 Ga 0.55 As/GaAs sample, which is known to be the state-of-the-art structure of dielectrics/GaAs. Both the peak intensity and the peak width are very similar between the two. The results show an almost indistinguishable excellent quality between the Ga 2 O 3 ͑Gd 2 O 3 ͒/GaAs and the Al 0.45 Ga 0.55 As/GaAs samples. This demonstrates the superiority of the Ga 2 O 3 ͑Gd 2 O 3 ͒/GaAs structure and supports further the reported successfully manufactured GaAs metal-oxide-semiconductor field-effect transistors using this Ga 2 O 3 ͑Gd 2 O 3 ͒ as the gate oxide.