Threshold reduction in Pb1−xSnx Te laser diodes through the use of double heterojunction geometries

Abstract

A systematic study has been made of the effect of the middle active region width in double heterojunction Pb1−xSnx Te/PbTe laser diodes on the lasing threshold. A fourfold reduction in pulsed threshold over that of comparable single heterojunction lasers is demonstrated in lasers having 4-μm-wide middle regions. A comparison is also made between lasers fabricated by liquid phase epitaxy using undoped melts and substrates, and using thallium-doped p -type PbTe layers; the latter is shown to yield thresholds as much as two times lower.

Lead-tin telluride double-heterojunction laser diodes: Theory and experiment

“…laser diodes. We will then present a more detailed model which is in agreement with the experimental results measured in this program [3] and by others [4], [ 5 ] . From this model we can begin to identify the parameters that will be important to further reduce threshold current densities, and can make more realistic predictions concerning high-temperature operation of Pb, -, Sn, Te laser diodes.…”

“…Growth, fabrication, and testing details as well as threshold current density dependence on active region thickness have previously been reported [3] for these devices without an attempt to compare the experimental results with theory.…”

“…8 experimental threshold data [3] have been plotted on the same graph with the curves from Fig. 5 which were theoretical calculations for a similar device.…”

“…1, in reducing semiconductor diode laser threshold current densities has been well documented in the (Ga, A1)As alloy system [ l ] . Heterojunction geometries have also very recently been used in Pb-salt diode lasers, specifically in the Pb (S, Se) [Z] and (Pb, Sn)Te [3] - [5] alloy systems. Significant systematic reduction of threshold current densities in DH (Pb, Sn)Te laser diodes has recently been demonstrated by Tomasetta and Fonstad [ 3 ] and continuous operation of (Pb, Sn)Te laser diodes at 77 K has been achieved by Groves et al with the aid of the DH geometry and careful heat sinking [SI .…”

Growth of Tl doped PbTe single crystals by the travelling heater method

“…The average temperature gradient at the has been a certain interest in thallium doped PbTe solid-liquid interface was measured to be apas a substrate material for lead tin telluride laser diodes [5,6]. We prepared TI doped PbTe single crystals of high structural perfection, i.e., without loweringl ow-angle boundaries which have been shown to mechanism usually result with Bridgman grown crystals of the same material [7].…”