Electrical and Optical Properties of GaAs Injection Lasers with Closely Compensated p-Type Region

Abstract

Results are presented of a detailed study of the electrical and optical properties of GaAs injection lasers fabricated by the liquid phase epitaxy method with heavily doped, closely compensated p regions (Zn∼10²⁰ cm⁻³, Sn∼5×10¹⁹ cm⁻³). The effects of various heat treatment steps were investigated to elucidate the role of injection and tunneling. The optical emission of the untreated diodes is centered at ∼9600 Å (300°K) and is thus considerably displaced from the bandgap energy. Despite the fact that internal absorption should be small in these devices, the external radiative efficiency is generally low at moderate current densities. Non‐radiative tunneling currents are shown to dominate charge transfer over a large range of forward bias. After heat treatment, the spontaneous efficiency improves and simultaneous stimulated emission at two wavelengths separated by 400 Å is observed at low temperatures. These emission bands are shown to originate in p‐type regions adjoining the junction differing in their degree of doping and of compensation. The threshold current density for lasing in the heavily doped, closely compensated region is considerably higher than for the more lightly doped, less compensated region.