Mid-infrared diode lasers
Type I strained InGaSb QW on GaAs

TSB project (TP11/LCE/6/I/AE096F)

We are using strained layer engineering at the nano-scale to develop a novel laser with a highly efficient active region containing InAlSb/InSb quantum wells. The proposed structure (Fig. 1) implements highly strained InGaSb QWs grown by MBE.

Figure 1
Figure 1 The layer structure (left) of the strained QW laser structure and the band diagram (right).

Figure 2
Figure 2 A typical diode laser spectrum: these lasers currently operate up to 220 K in pulsed mode.

Figure 3
The effect of compressive strain on the in-plane and perpendicular band structures of III-V semiconductors is illustrated in Figure 3 (right). The use of type-I strained MQW lasers on high quality GaAs substrates has not been previously investigated. The advantages of this approach are: equalisation of electron-hole densities of states leading to a reduction of inter-valence band absorption, suppression of the dominant Auger recombination processes, and increased valence band offset within the strained quantum wells to reduce hole leakage.