1 February 2013
Publication year: 2013
Source:Journal of Crystal Growth, Volume 364
Compositionally step-graded ((Al)Ga) x In1−x P (x =0.52–0.22) buffers and following In0.3 Ga0.7 As cap layers are grown by metal-organic chemical vapor deposition on (001) GaAs substrates with different miscuts toward (111)A. The tilt with respect to the substrate and phase separation in Ga x In1−x P buffer layers are investigated by x-ray reciprocal space mapping and transmission electron microscopy. It is found that a large negative tilt is generated in the [110] direction due to the preferential nucleation of α dislocations with tilt component along [001¯], and that a positive tilt in the [11¯0] direction is introduced by the wavy surface undulations along [11¯0] when growing the Ga x In1−x P buffer and enhanced by preferential glide of the existing β dislocations in the (1¯11) slip plane during the growth of the In0.3 Ga0.7 As cap layer. The phase separation in the Ga x In1−x P buffer layer, acting as the main source of threading dislocations in the In0.3 Ga0.7 As cap layer, has been suppressed by increasing the number of steps in the buffer layer and thickness and utilizing (Al0.3 Ga0.7 )0.22 In0.78 P layer as the top buffer layer. Finally, In0.3 Ga0.7 As layers with a low threading dislocation density are obtained on the top AlGaInP layer due to the lattice hardening effect and this improvement is confirmed by the photoluminescence measurements.
► Metamorphic (Al)GaInP buffers were grown by MOCVD. ► Large tilt was generated in [110] direction due to substrate miscut. ► The wavy surface and inequality of β dislocation glide introduce tilt in [11¯0]. ► AlGaInP can effectively suppress phase separation in the buffer. ► InGaAs cap layer with a low density threading dislocations was obtained.
Publication year: 2013
Source:Journal of Crystal Growth, Volume 364