On the performance of selenium rich lead-salt heterostructure lasers with remote p-n junction

In order to increase the operating temperature of lasers emitting in the mid-IR, various lead chalcogenide diode lasers have been fabricated and examined: Pb
0.95
Sn
0.05
Se/PbSe and PbSe/PbS double heterostructure and funnel-type Pb
1-x
Eu
x
Se lasers (the Eu content in the cladding layers increased steadily from
x = 0.01
near the active layer up to
x = 0.03
). All the lasers were grown by molecular beam epitaxy on PbSe substrates. The p-n junctions were located not on the (lattice mismatched) interfaces, but at various distances (2000-6000 A) within the confinement layer. The highest operation temperatures (CW operation up to 165 K at 5.3 μm and pulsed operation up to 220 K at 4.4 μm) were attained by the PbSe/Pb
1-x
Eu
x
Se funnel-type laser. The experimental results were compared to theoretical computer-assisted calculations, which accounted in a self-consistent way for the distributions of light, charge carriers, and temperature within the lasers. The agreement between theory and measurements for the temperature dependence of the threshold current and wavelength and for maximal operation temperatures was quite good. We found that the main contributions to the current come from interface recombination and from overbarrier leakage of nonconfined carriers (both minority and majority). Ways to improve the lasers are discussed.