We report on diffusion-driven and excitation-dependent carrier recombination rate in multiple InGaN/GaN quantum wells by using photoluminescence, light-induced absorption, and diffraction techniques. We demonstrate gradually increasing with excitation carrier diffusivity and its correlation with the recombination rate. At low carrier densities, an increase in radiative emission and carrier lifetime was observed due to partial saturation of non-radiative recombination centers. However, at carrier densities above ∼5 × 1018 cm−3, a typical value of photoluminescence efficiency droop, a further increase of diffusivity forces the delocalized carriers to face higher number of fast non-radiative recombination centers leading to an increase of non-radiative losses.

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Growth of blue InGaN based LED structures on sapphire wafers from 2 inch to 8 inch in diameter was investigated using the Veeco K465 MOCVD platform. Our results indicate that the same pressure, rotation rate and hydride flows can be used for all wafer sizes. AFM and X-ray studies reveal that all wafer sizes have comparable high-quality crystallinity and defect levels for GaN and InGaN/GaN MQW growth. Although the larger diameter wafers exhibit larger wafer bow due to lattice and thermal mismatch, with proper wafer pocket design, good wavelength and thickness uniformity can be obtained for all wafer sizes. GaN, InGaN, blue LED, MOCVD Citation:Lu F, Lee D, Byrnes D, et al. Blue LED growth from 2 inch to 8 inch.

We have grown InAs QDs on two types of vicinal GaAs substrates and under various growth conditions. QDs grown on 2° offcut substrates show superior optical characteristics compared to QDs on 6° offcut substrates, which showed no QD luminescence. The InAs growth temperature was shown to have an impact on QD nucleation, with higher growth temperature leading to both improved dot densities and coherence. Finally, the V/III ratio during InAs growth dramatically effects the uniformity of the QD luminescence. Our best QDs were grown at 495°C using a V/III ratio of 12. These QDs were 7×40nm in size with a density of 5(±0.5)×10 10 cm -2 . The spatial PL, peaking at 1220 nm, had a wavelength and intensity deviation across the 2" wafer of 0.3% and 16%, respectively.

Blue light-emitting diodes (LED's), utilizing InGaN-based multi-quantum well (MQW) active regions deposited by organometallic chemical vapor epitaxy (OMVPE), are one of the fundamental building-blocks for current solid-state lighting applications. Studies [1,2] have previously been conducted to explore the optical and physical properties of the active MQW's over a variety of different OMVPE growth conditions. However, the conclusions of these papers have often been contradictory, possibly due to a limited data set or lack of understanding of the fundamental fluid dynamics and gas-phase chemistry that occurs during the deposition process.Multi-quantum well structures grown over a range of pressures from typical low-pressure production processes at 200 Torr, up to near-atmospheric growth conditions at 700 Torr, have been investigated in this study. At all growth pressures, clear trends of gas-phase chemical reactions are observed for increased gas residence times (lower gas speeds from the injector flange and lower rotation rates) and increased V/III ratios (higher NH 3 flows).Confocal microscopy, excitation-dependent PL (PLE), and time-resolved photoluminescence (TRPL) have been employed on these MQW structures to investigate the carrier lifetime characteristics. Confocal emission images show spatially-separated bright and dark regions. The bright regions are red-shifted in wavelength relative to the dark regions, suggesting microscopic spatial localization of high indium content regions. As the growth pressure and gas residence times are reduced, a larger difference in band-gap between bright and dark regions, longer lifetimes, and higher average PL intensities can be obtained, indicating that higher optical quality material can be realized. Optimized MQW's grown at high pressure exhibit higher PLE slope intensities and IQE characteristics than lower pressure samples. Results on simple LED structures indicate that the improvement in MQW optical quality at high pressures translates to higher output power at a 110 A/cm 2 injection current density. 505