Single heterojunction Pb/sub 1-X/Sn/sub x/Te diode lasers

Single heterojunction diode lasers in the Pb1−xSnx Te alloy system have been fabricated by low-temperature vacuum deposition of n-PbTe on a p-Pb0.88Sn0.12 Te substrate. The lasers have lower threshold current densities and operate cw at higher temperatures than homojunction devices in this material. At laser threshold the incremental diode resistance drops abruptly from 0.5 Ω to a series resistance limited value of 0.08 Ω, a previously unobserved effect in diode lasers which indicates very high internal quantum efficiency.