InGaN系半導体デバイスの発光機構(<特集>半導体エレクトロニクス)

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Dynamics of spontaneous and stimulated emissions in InGaN-based laser-diode (LD) structures have been assessed by employing time-resolved photoluminescence (TRPL) and pump & probe (P & P) spectroscopy at room temperature. The LDs are composed of In_xGa_1-xN-In_yGa_1-yN MQWs[(a) : x=0.1, y=0.02, (b) : x=0.2, y=0.05], whose stimulated emissions correspond to near ultraviolet (390nm) and violet (420nm), respectively. Almost no Stokes shift was observed for the sample (a) (x=10%). However, Stokes shift in the sample (b) (x=20%) was as large as 250meV, and it is probable that the origin of such deep localization is In-rich quantum dots self-formed during the growth. It is likely that large internal quantum efficiency in In-rich In_xGa_1-xN active layers is as a result of zero-dimensionality because capture-cross-section to non-radiative recombination centers are greatly reduced once excitons are trapped at deep localization centers. P & P spectroscopy has revealed that the optical gain was contributed from the nearly delocalized states [the lowest-quantized MQW levels (LQL)] in the sample (a), while it was from highly localized levels with respect to LQL by 250meV for the sample (b). It was found that the photo-generated carriers rapidly (within a few hundred fs) transferred to LQL, and then relaxed to the localized tail within the time-scale of a few ps, giving rise to the optical gain. Such gain spectra were saturated and other bands appeared in the vicinity of LQL under higher photo-excitation.
社団法人日本材料学会の論文
2001-04-15

InGaN系半導体デバイスの発光機構(<特集>半導体エレクトロニクス)

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