D − centers in intracenter Si:P lasers

Abstract

The terahertz Si:P laser is based on the 2p0→1s(T2) transition of neutral phosphorus donors D0 that are photoionized by radiation from a CO2 laser. The manifestation of negatively charged D− donor centers has been studied. The population of D− centers as well as D0 donor states are calculated and the amplification provided by D0 centers is compared with the absorption by D− centers. The small signal gain and laser threshold have been measured for a set of Si:P lasers with different degrees of compensation (doping by neutron transmutation). It is shown that absorption by D− centers terminates the laser action in Si:P lasers with small compensation (K<1%) for pump intensities less than 1kWcm−2. At higher excitation levels (>10kWcm−2), or for larger compensation, absorption by D− centers becomes negligible.