InP/InAlGaAs light-emitting transistors and transistor lasers with a carbon-doped base layer

Characteristics of InP/InAlGaAs light-emitting transistors (LETs) and transistor lasers (TLs) using carbon (C) for p-type doping of the base region were investigated. The N-InP/p-In_0.52(Al_0.4Ga_0.6)_0.48As/N-In_0.52Al_0.48As LETs show a current gain of 0.22 and light emission at wavelength of λ ∼ 1610 nm. The low current gain is attributed to the short minority carrier lifetime in the C-doped base with a quantum well. The TL demonstrates continuous-wave operation at −190 °C with a threshold current of I_B = 35 mA. By comparing the optical output characteristics of the TL and a laser diode with similar structure, it is suggested that the low differential quantum efficiency and the high threshold current density in the TL is related to the strong inter-valence band absorption in the heavily doped base layer.