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We have measured the time response of the emission spectra of In0.07Ga0.93N quantum wells with widths of 2, 3, and 4 nm in GaN following pulsed optical excitation. We observe a blue shift of the emission peak during the excitation and a subsequent red shift as the carriers recombine in the 3- and 4-nm wells, and a negligible shift for the 2-nm well. Using a comprehensive theory we are able to fit both the time evolution of the peak emission energy and the integrated emission intensity. The shift of the emission peak (by about 17 meV) arises from the balancing of the change in screening of the internal piezoelectric field as the carrier density changes and bandgap renormalization. We have projected the calculations to quantify the degree of screening at typical threshold carrier densities. At transparency we estimate carrier densities of 4.3 × 1016 m-2 and 4.8 × 1016 m-2 for the 4- and 3-nm wells, respectively, which reduce the internal piezoelectric field in the well to 0.97 × 108 (4 nm) and 1.03 × 108 (3 nm) V·m-1 compared with the unscreened value of about 1.23 × 108 V·m-1. Thus, a substantial field remains in these wells under laser conditions. We find that this partially screened field is beneficial in reducing the threshold current compared with that of a square well for modal gains up to about 150 cm-1. [ABSTRACT FROM AUTHOR]

Reports on CW optical investigations of the carrier transport mechanisms in a double quantum-well (QW) InGaAs-InGaAsP-InGaP laser diode developed to emit record-high values of radiant power around 970 nm. Escape channel that limits carrier emission of the QWs; Steady-state carrier capture processes in the active region of a fully operational laser diode.

Carrier localization in InGaN/GaN multiple-quantum wells (MQWs) with three different well thicknesses was investigated optically using time-integrated and time-resolved microphotoluminescence spectroscopy. An anomalous temperature dependence of the photoluminescence peak energy was observed, as a consequence of local potential fluctuations. The carrier localization was more prominent in the case of MQWs with wide well thickness. The results indicate that the degree of potential fluctuation increases with increasing well thickness. Emission from quantum-dot-like states only became apparent in MQWs with wide well thickness, which supports the assertion that carrier localization in InGaN/GaN MQWs is due to the formation of quantum dots. [ABSTRACT FROM AUTHOR]