Yellow In1−xGaxP1−zAsz double-heterojunction lasers

Abstract

Improved yellow‐spectrum double‐heterojunction In_1−xGa_xP_1−zAs_z laser diodes constructed by LPE on VPE GaAs_1−yP_y substrates are described. The lattice‐matched LPE quaternary alloy growth process is outlined, as well as the need for complete melt removal between the growth of each heterojunction layer, which is more difficult for In‐rich melts than for Ga‐rich melts when lattice match is a problem. Over two times lower threshold current densities are demonstrated (J_th?3.6×10³ A/cm², λ?5920 Å, 77 °K) than for the first reported diodes of this type. The temperature dependence of laser threshold current density is presented in the range 4.2–200 °K. The threshold current density can be approximated as J_th∝exp(T/T₀) with T₀?52 °K in the range 50–175 °K, which compares well with red‐orange AlGaAs double heterojunctions (T₀?42 °K) having greater heterobarriers. Laser operation in the yellow‐orange portion of the visible spectrum at ∼200 °K is demonstrated. These results on thick (1.5 μm) active layer diodes, having relatively small heterobarriers (ΔE∼65 meV), indicate that further improvement and control of the quaternary growth process will lead to still lower threshold currents and higher‐temperature operation in the orange‐yellow.