We report on the growth of GaN in GSMBE using NH3 as nitrogen source. Special focus will be on the NH3 cracking, where we applied an On Surface Cracking technique (OSC). Using OSC we achieve photoluminescence linewidths as narrow as 5.5meV (5K) and mobilities of 220 cm2/Vs at room temperature.

Ultra-thin oxynitrides can serve as gate dielectrics for the technology nodes 100 nm and below. In this work, we present the properties of ultra-thin oxynitride gate dielectrics prepared by RTP nitridation of Si in NH3 followed by post-grown oxidation in O-2 or in steam (post nitridation anneal, PNA). The layers show excellent barrier properties including significantly lower leakage current compared to SiO2 Of identical equivalent oxide thickness (EOT). For the same EOT, the tunnel current density of the RTP oxynitride layers were about four orders of magnitude lower compared to SiO2, With optimised, the interface state density (D-it) of the RTP-grown oxynitride layer is in the region of a good SiO2 layer (D-it, similar to 1E11 eV(-1) cm(2)). X-ray photoelectron spectroscopy (XPS) data of selected oxynitride layers indicate that a nitrogen concentration of as high as 31% can be achieved by RTP process. RTP grown oxynitride layers were applied to NMOS transistors as gate dielectrics and their device performances were compared with those prepared by RF plasma nitridation (RF-PN). Transistors with RTP-grown oxynitride gate show a significantly better uniformity in threshold voltage on 200 mm wafers than those oxynitride layers grown by RF-PN. It was also found that the leakage currents of the RTP and RF-PN gate oxynitrides obey the same trend from the 1.5.nm EOT regime down to the 1.0 nm EOT regime. This observation indicates that the leakage current barrier quality of the RTP oxynitride is at least as good as the RF-PN oxynitrides. (c) 2004 Elsevier B.V. All rights reserved.

In this article, multiple-step rapid thermal annealing (RTA) processes for the activation of Mg doped GaN are compared with conventional single-step RTA processes. The investigated multiple-step processes consist of a low temperature annealing step at temperatures between 350°C and 700°C with dwell times up to 5min and a short time high temperature step. With optimized process parameters, and multiple-step processes, we achieved p-type free carrier concentrations up to 1–2×1018cm−3. The best achieved conductivity, so far, lies at 1.2Ω−1cm−1. This is a 50% improvement compared to conventional single-step process at 800°C, 10min.

Using hydride vapor phase epitaxy the influence of growth parameters on the crack density is studied for thick epitaxially lateral overgrown (ELOG) GaN layers. Reactor pressure, growth rate, and substrate temperature are key factors to obtain crack-free thick GaN layers. The cracking mechanism is discussed and void formation on top of the SiO2 stripes is proposed to play a key role in stress relaxation and crack suppression.

In this paper, Hydride Vapour Phase Epitaxy (HVPE) of GaN layers under reduced pressures is reported. First results show that the HVPE grown GaN layers exhibit excellent electrical, crystallographic and optical quality. By reducing the reactor pressure from 950 to 250 mbar, improvements in background doping (down to 2 x 10(16) cm(-3)) and Hall mobility (up to 300 cm(2)/Vs) are observed. Experiments on MOVPE overgrowth on HVPE GaN layers show excellent results. Low temperature PL spectra of the overgrowth MOVPE layer reveal all three free exciton levels (FE A, FE B, FE C) without any visible bound excitons.

We report the successful fabrication of the first gas source MBE grown InAsP/InGaAsP multiple-quantum well lasers with compositional linearly graded InGaAsP confinement layers. The optical quality of the InAsP/InGaAsP quantum wells are investigated by room temperature photoluminesence (PL) spectroscopy; Intense PL-signal with small FWHM is observed in structures containing three quantum wells indicating that our structures are of high optical quality. Nonlinear temperature-ramps are developed and applied to the gallium effusion cell in order to grow lattice-match compositional linearly graded InGaAsP confinement layers. X-ray rocking curves show that the lattice-mismatches of the graded InGaAsP confinement layers. X-ray rocking curves show that the lattice-mismatches of the graded InGaAsP layers are well below 1×10−3. These results indicate that the control of material supply during growth of the InGaAsP layers is highly precise. Laser structures containing graded confinement layers and three quantum wells are grown and fabricated into broad-area laser diodes. Threshold current density of 160Acm−2 was obtained for 1.5mm long lasers. This value is among the lowest ever achieved for 1.3μm lasers grown by any kind of MBE process.

Epitaxial GaN films have been grown on inert- and active-side GaN bulk substrates using reactive MBE, where ammonia is cracked on the substrate surface. We achieved state-of-the-art optical properties as proved by extremely narrow linewidths in low-temperature photoluminescence. Transitions of excitons bound to neutral donors at 3.4709 and 3.4718eV are as narrow as 0.5meV. Additionally, the suitability of the RMBE approach for optoelectronic devices is demonstrated with electroluminescence of ultra-violet light-emitting diodes at 371nm with linewidths of 8nm.

We report the successful fabrication of the first Gas Source MBE grown InAsP/InGaAsP single and multiquantum well lasers with linearly graded InGaAsP confinement layers. The optical quality of the InAsP/InGaAsP quantum wells (QWs) are investigated by room temperature Photoluminescence (PL) spectroscopy; Intense PL-signal with small FWHM is observed in structures containing five, three and one quantum well indicating that our structures are of high optical quality. Laser structures containing graded confinement layers and various numbers of quantum wells are grown and fabricated into broad-area laser diodes. Threshold current densities of 400 A/cm/sup 2/ 270 A/cm/sup 2/ and 180 A/cm/sup 2/ are obtained for 1.2 mm long lasers containing five, three and single quantum well, respectively. These values are among the lowest ever achieved for 1.3 /spl mu/m lasers grown by any kind of MBE.