Suppression of defect propagation in semiconductors by pseudomorphic layers
The propagation of defects in semiconductor heterostructures has been studied both theoretically and experimentally. The simple model shows that defects originating from lattice‐matched regions can be prevented from entering, or can be trapped by, a pseudomorphic layer, depending on the signs of the strain induced by the defect and the strain in the pseudomorphic layer. A pseudomorphic layer can therefore prevent the defect from propagating across in and entering the critical active region of a device. Experimentally, the photoluminescence intensities of Al0.4Ga0.6As/GaAs quantum wells with and without pseudomorphic In0.2Ga0.8As layers for prevention of defect propagation have been compared. GaAs substrates of high etch pit density were used to generate defects below the quantum well and silicon implantation was used to generate defects above it. The elevated temperatures during molecular‐beam‐epitaxial growth and postimplant rapid thermal annealing serve to assist in defect propagation in the respective ...
Reduction of Be out‐diffusion from heavily doped GaAs:Be layers by pseudomorphic InxGa1−xAs barrier layers
The effectiveness of suppressing Be out‐diffusion from a Be‐doped GaAs layer by strained InGaAs layers using secondary ion mass spectroscopy has been evaluated. The experimental structures consist of an 800 A Be‐doped (∼1×1019 cm−3) GaAs layer sandwiched between 80 A InxGa1−xAs (x=0,0.1,0.25) layers. The samples were subjected to rapid thermal annealing (RTA) at 750 °C for 6 min. It is clearly observed that Be diffusion beyond the InGaAs layers is the fastest for the structure with x=0 and the slowest for the structure with x=0.25.
AlInGaAs/AlGaAs separate‐confinement heterostructure strained single quantum well diode lasers grown by organometallic vapor phase epitaxy
Separate‐confinement heterostructure diode lasers containing a strained Al0.18In0.20Ga0.62 As single quantum well active layer and Al0.25Ga0.75As confining layers have been fabricated from structures grown on GaAs substrates by low‐pressure organometallic vapor phase epitaxy. The emission wavelength of these devices is 814 nm. Threshold current density is as low as 103 A cm−2 for cavity length L=1500 μm, and differential quantum efficiency as high as 90% for L=280 μm. The characteristic temperature T0 is 214 K between 10 and 40 °C, and 159 K between 40 and 80 °C. Preliminary tests of cw operation suggest that these lasers are more reliable than AlGaAs/AlGaAs lasers.