K. Umeno

Direct observation of N-(group V) bonding defects in dilute nitride semiconductors using hard x-ray photoelectron spectroscopy

Using bulk sensitive hard x-ray photoelectron spectroscopy, we directly observe a spectrum related to N–As bonding defects in (Ga,In)(N,As)/Ga(N,As) heterostructure. The defects are most likely attributed to split interstitials. Their concentration is in the order of 1019 cm−3, close to the detection limit of the measurement. Rapid thermal annealing eliminates the defects, leading to those undetectable. Similar phenomenon is observed for N–P bonding defects in In(N,P). The results indicate common features in dilute nitride semiconductor system: existence of N-(group V) bonding defects and their behavior on postgrowth annealing.

Effect of Indium on Photoluminescence Properties of InGaPN Layers Grown by Solid Source Molecular Beam Epitaxy

The effect of indium on photoluminescence properties of InGaPN layers was investigated and compared with that of GaPN layers. Two phenomena involving photoluminescence properties were observed in the InGaPN layers: (i) an S-shape of photoluminescence (PL) peak energy as a function of temperature, caused by spatial fluctuation of bandgap energy related to In and N content; and (ii) red shifts of the PL peak energy at 18 K in the InGaPN layers after rapid thermal annealing (RTA), caused by the increase of N- and In-rich region with increasing RTA temperature. It was also found that integrated PL intensity in the InGaPN layers was higher than that in the GaPN layers, and that PL quenching became more insensitive to the change in temperature resulting from the decrease in nonradiative centers with increasing RTA temperature.

Growth and luminescence characterization of dilute InPN alloys grown by molecular beam epitaxy

The authors have investigated the growth and luminescence properties of InPN alloys grown by solid-source molecular-beam epitaxy (MBE). The N composition increases with decreasing growth rate, P2∕In flux ratio, and growth temperature. In this work, the highest N composition obtained is 0.56% for the InPN sample. The appropriate growth temperature is around 400°C. However, the growth-temperature window of the InPN alloys having a smooth surface is very narrow. In order to obtain photoluminescence (PL) emission from the InPN samples grown by solid-source MBE, InPN alloys must be grown under the condition of lower-plasma power since the grown-in point defects induced by N plasma are reduced. Thermal treatment is effective to improve the luminescence efficiency of InPN alloys, and the appropriate annealing temperature is around 700°C. However, the S-shape behavior is observed only for the annealed InPN samples by atomic rearrangements during thermal treatment, which is attributed to the weaker bond strength o...

Infrared Absorption Spectrum of InNP

The infrared (IR) absorption spectra of InNxP1-x (x= 0.19–0.56%) grown on an InP substrate are investigated by Fourier-transform infrared (FT-IR) spectroscopy. The optical phonon corresponding to the In–N bond in InNP has an energy of 456 cm-1. This energy matches the reported value for the optical phonon energy of In–N bonds in GaInNAs. It is very close to the transverse optical (TO) phonon energy in pure cubic InN. It contrasts with the fact that the optical phonon energy of Ga–N bonds in GaInNAs is lower by 85 cm-1 in comparison with the TO phonon energy in pure cubic GaN. Thermal annealing hardly affects the phonon spectrum of InNP, although it improves the crystallinity of the semiconductor.