Free Carrier Radiative Recombination in 2D: PbTe Quantum Wells

There have been a number of studies aimed at isolating radiative recombination in semiconductor quantum wells, a process which in many instances is strongly influenced by excitonic effects such as in III-V (e.g. GaAs [1]) or wide-gap II-VI (e.g. ZnSe [2]) semiconductor heterostructures. Recently, Matsusue and Sakaki have exploited modulation doped GaAs/(Ga,Al)As multiple quantum wells (MQW) to show how radiative recombination of a quasi-two dimensional (2D) free electron-hole gas can be distinctly identified while reducing excitonic complications [3]. In narrow-gap semiconductors, such as PbTe, excitonic effects are negligible; therefore quantum wells from these materials offer a clear opportunity to study quasi-2D free carrier radiative recombination over a wide temperature and density. We show here that radiative recombination dominates in high quality MBE-grown PbTe/(Pb,Eu)Te MQW’s. At the same time PbTe/(Pb,Eu)Te based heterostructures show excellent prospects as low threshold diode injection lasers at mid-infrared wavelengths [4].