Observation of long photoluminescence decay times for high-quality GaN grown by metalorganic chemical vapor deposition

Abstract

GaN epitaxial layers with different crystalline quality grown on sapphire substrates by metalorganic chemical vapor deposition are investigated using time-resolved photoluminescence at 300 K. It is found that the time-dependent photoluminescence of low-quality GaN decays faster than that of the high-quality GaN films. The time constants for the dual-exponential decay of the photoluminescence are calculated to be 50 and 250 ps for high-quality undoped GaN and 30 ps for low-quality undoped GaN. For high-quality Si-doped GaN, time constants of 150 and 740 ps are extracted while corresponding time constants of 40 and 200 ps are measured for low-quality Si-doped GaN. We believe that the time constant of 740 ps measured for our high-quality Si-doped GaN is the longest ever reported for thin GaN/sapphire films.

Growth of AlGaN alloys exhibiting enhanced luminescence efficiency

“…The intermediate defect density sample's lifetime is comparable to that measured for high-quality GaN. 10 Moreover, the NCI emission from the low-defect density sample is significantly larger than the ;500-ps lifetime observed for our high-quality PA-MBE GaN deposited on HVPE-grown GaN with dislocation density of ;10 7 cm ÿ2 . 9 These results suggest that while these NCI regions can effectively compete with dislocations in these materials, their performance can be significantly enhanced through the reduction of such defects.…”

Suppression of non‐radiative effects in AlGaN through nanometer scale compositional inhomogeneities

“…Consistent with this result, time-resolved photoluminescence measurements indicated a PL lifetime of 290 and 650 ps in the intermediate and low defect density samples, respectively, while the highest defect density sample had a system-limited (< 20 ps) PL lifetime. The intermediate defect density sample's lifetime is comparable to that measured for high quality GaN grown by metalorganic chemical vapor deposition on sapphire substrates [9]. Moreover, the NCI PL lifetime from the low defect density sample is significantly larger than the ~ 500 ps PL lifetime observed for our high quality PA-MBE GaN deposited on HVPE-grown GaN with dislocation density of ~ 10 7 cm -2 [10].…”

Investigation of nanopatterned c-plane sapphire Substrates for Growths of polar and nonpolar GaN epilayers

“…The curve fitting results reveal that Sample C has the longest relaxation time (246 ps and 857 ps) than the other two samples (154 ps and 184 ps for Sample A and Sample B, respectively). The shorter lifetime of Samples A is attributed to the trapping of photoexcited carriers in the nonradiative TDs (line defects) [36]. The experimental evidence to support this argument is the reduction of dislocation density in the GaN epilayer grown on the c-NPSS and therefore the enhancement of band-edge PL.…”