The effect of N-doping of MQWS on the properties of deep ridge transistor lasers

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.