Transistor lasers (TLs) with n-doped quantum wells (QWs), which own low threshold current, are reported in this paper. The exposed side walls of QWs introduce amounts of recombination centers, which damages the properties of deep ridge TLs greatly. It is found that the heavily doping in quantum wells can effectively alleviate this effect.
Assuming that the surface recombination is 106 cm/s, the light output power and current gain of common emitter configurations as functions of varying doping concentration and ridge width are studied. With doping concentration of 1018 cm−3 and ridge width of 2µm, the threshold current of TLs can be reduced from more than 100 mA to 31 mA and current gain can be increased from 0.1 to 2.4.