Influence of doping on threshold current of semiconductor lasers

Doping of the active layer of a semiconductor laser reduces the threshold carrier density, the more so the higher the doping level. As a consequence, the threshold current goes through a minimum dependent on doping. This minimum arises for doping densities of the order of 1018 cm¿3, and lies about 25% below the value without doping for an n-doped InGaAsP laser. As the temperature dependence of the threshold current is simultaneously weaker (T0¿85°), appropriate n-doping may improve the efficiency of a semiconductor laser. Additionally, it is shown that n-doping is more favourable than p-doping.