Abstract
Separate continement heterostructure (SCH) laser material was grown by metalorganic chemical vapor deposition (MOCVD) with a 50-Å thick GaAs single-quantum-well (SQW) active layer sandwiched between 2200-Å thick graded refractive-index (GRIN) AlGaAs layers. Sixty micron wide oxide-defined stripe lasers with uncoated facets were fabricated, and the pulsed power output vs current characteristics measured for various length devices held at a heat sink temperature of 30°C. The average threshold current lth vs length L data derived from these measurements is shown in Fig. 1. Also shown for comparison purposes is lth vs L data for relatively thick active-layer (0.15-μm) double-heterostructure (DH) lasers grown by MOCVD in the same reactor. As expected, %, for the DH lasers decreases linearly as L decreases, whereas lth for the GRIN-SCH-SQW lasers has an unexpected increase as L decreases below 300 μm. Another unexpected feature of the GRIN-SCH-SQW data is the <10% change in lth as L is increased from 300 to 600 μm. By varying the heat sink temperature between 20 and 80°C, additional lth vs L data were obtained from which was extracted characteristic temperature1 T0 information. It was found that T0 decreases from a high of 230 K for the 600-μm long devices to a low value of 60 K for the 150-μm long devices. Modeling work indicates that basic radiative recombination theory in the high-gain regime2 is not sufficient to explain quantitatively these results. Models which include additional mechanisms such as L-band filling3 are required. Additional data will be presented, and the physical mechanisms possibly responsible for this anomalous threshold behavior discussed.
© 1986 Optical Society of America
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