Threading Dislocation Densities in GaAs Grown on Reduced Area Si Substrates

Transmission electron microscopy is applied to investigate the effect of post-annealing on misfit dislocations in an In0.2Ga0.8As/GaAs(001) heterostructure. An orthogonal array of 60° dislocations along [110] and % MathType!MTEF!2!1!+- % feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqr1ngB % PrgifHhDYfgasaacH8srps0lbbf9q8WrFfeuY-Hhbbf9v8qqaqFr0x % c9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8fr % Fve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaadaWada % qaaiaaigdaceaIXaGbaebacaaIWaaacaGLBbGaayzxaaaaaa!3BE5! $$\left[ {1\bar 10} \right]$$ directions was observed in the interfaces of the samples grown by MBE at 520 °C. When the as-grown samples were annealed at temperatures ranging from 600 to 800 °C, the 60° dislocations were gradually reoriented by dislocation reactions occurring at the 90° intersections followed by nonconservative motion driven by dislocation line tension and the residual elastic misfit strain. The final result of this process was a dislocation array lying along [100] and [010] directions. The reoriented u =<100> dislocation has a Burgers vector % MathType!MTEF!2!1!+- % feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqr1ngB % PrgifHhDYfgasaacH8srps0lbbf9q8WrFfeuY-Hhbbf9v8qqaqFr0x % c9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8fr % Fve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWHIb % GaaeypamaalaaabaGaaeyyaaqaaiaaikdaaaGaeyipaWJaaGymaiaa % icdacaaIXaGaeyOpa4daaa!3F42! $${\bf{b}}{\text{ = }}\frac{{\text{a}}}{2} < 101 >$$ , which is the same as that of 60° dislocation, but the edge component of its Burgers vector in the (001) interfacial plane is larger than that of 60° dislocation by a factor of % MathType!MTEF!2!1!+- % feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqr1ngB % PrgifHhDYfgasaacH8srps0lbbf9q8WrFfeuY-Hhbbf9v8qqaqFr0x % c9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8fr % Fve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaadaGcaa % qaaiaaikdaaSqabaaaaa!3882! $$\sqrt 2 $$ , resulting in a greater contribution to elastic strain relaxation. This nonconservative reorientation of 60° dislocations to form the u=<100> dislocations represents a new strain relaxation mechanism in diamond or zinc blende semiconductor heterostructures.