Continuous-wave (cw) indium-gallium nitride (InGaN) multiple-quantum-well (MQW) laser diodes (LDs) were successfully transferred from sapphire onto copper and diamond substrates using a two-step laser lift-off (LLO) process. Reduced threshold currents and increased differential quantum efficiencies were measured for LDs on Cu due to a 50% reduction of the thermal impedance. Light output for LDs on Cu was three times greater than comparable LDs on sapphire with a maximum output of 30 mW. Increased light output for LDs on diamond were also measure with a maximum output of 80 mW.

High peak electron mobilities were observed in free-standing c-plane GaN substrates. Two layers, a low mobility degenerate layer and a high mobility bulk layer, were present in these samples. The carrier concentrations and mobilities for the layers were extracted using two methods: 1) magnetic field dependent Hall effect analysis and 2) a simple two carrier model with the assumption that one of the layers is degenerate. In addition, measurements were performed after etching away the degenerate layer. The mobility of the bulk layer is found to peak at nearly 8000 cm2/Vs at 60K using the magnetic field dependent Hall effect data. Record room temperature mobility for bulk GaN of 1190 cm2/V s was measured.

We studied and compared the emission properties of optically excited (Al)GaN structures grown by two different techniques: hydride vapor phase epitaxy (HVPE) and metalorganic chemical vapor deposition (MOCVD). We successfully achieved stimulated emission (SE) in an HVPE-grown GaN epilayer and a GaN/AlGaN double heterostructure at 10 K and room temperature. We found that the SE threshold and photoluminescence efficiency of the HVPE-grown samples are similar to those of high-quality MOCVD-grown structures. Photoluminescence measurements from 10 to 300 K show that the HVPE GaN has a high density of non-radiative recombination channels, especially those activated below 100 K. This study represents the first demonstration of SE in HVPE-grown (Al)GaN heterostructures.

Advanced high frequency devices using GaN-based semiconductor require the technology to form high resistivity regions with high thermal stability to electrically isolate the active elements from surroundings, as well as from the underlying substrate. The present paper describes the preparation of thermally stable, high resistivity GaN layers by ion implantation. It was confirmed that C or Zn implantation yielded high resistivity layers. In particular, Zn implantation yielded the layers with resistivity on the order of 1010 cm, which could be sustained at temperatures as high as 1000.

Localized vibrational modes of carbon-hydrogen complexes in metalorganic chemical vapor deposition grown GaN on sapphire were studied using a Fourier-transform infrared spectroscopy technique. Three distinctive localized vibrational modes were observed around 2850, 2922, and 2959 cm−1 for undoped, Si- and Mg-doped samples. These peaks are related to CH, CH2, and CH3 defect complexes, respectively. It is also observed that the frequencies and intensities of the localized vibrational modes are sample dependent.