GaAs–AlxGa1−xAs Double Heterostructure Lasers—Effect of Doping on Lasing Characteristics of GaAs

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Abstract
The GaAs–Al x Ga1−x As double heterostructure (DH) junction laser is shown to be a most suitable structure for studying lasing properties of GaAs as a result of complete optical and carrier confinement. Lasers fabricated from highly uniform DH wafers permitted accurate measurement of thresholds and efficiencies as a function of laser length. Thus the gain and loss for ``bulk'' GaAs at room temperature were determined for the first time without ambiguity. The gain was found to vary with current as g∝Jm , where m ranges from 1.5 to 3 depending on doping. At low excitation the gain is appreciably higher for lasers with heavily compensated active layers than for lasers with lightly dopedactive layers. The dependence of gain on current agrees qualitatively with the theoretical results of Stern and Hwang. The internal loss of the DH laser agrees approximately with the value which is estimated from passive free‐carrier absorption of bulk GaAs.