Dependence of Threshold Current Density and Efficiency on Fabry-Perot Cavity Parameters: Single Heterojunction (AlGa)As–GaAs Laser Diodes

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Abstract
A detailed study was made of the dependence of the threshold current density and the external differential quantum efficiency on the cavity end loss in single‐heterojunction laser diodes. To eliminate possible errors introduced by studying lasers of varying lengths, this study relied on changes of the facet reflectivity by SiO coatings of appropriate thickness. The results are consistent with a linear relationship between the threshold current density and the gain coefficient at threshold. The values of the gain factor, absorption coefficient, and internal quantum efficiency at 300 and 77°K are in excellent agreement with some of the previous studies. However, for effective end losses greater than ∼50 cm−1 the differential quantum efficiency shows an anomalous effect by decreasing with increasing end loss instead of increasing as predicted by simple theory. This effect occurs at 77°K as well as 300°K and is tentatively attributed to internal trapping of the stimulated emission.