THE GROWTH OF GAINAS/INP AND GAINAS/ALINAS SUPERLATTICES WITH THIN BARRIER LAYERS BY LOW-PRESSURE ORGANOMETALLIC CHEMICAL VAPOR-DEPOSITION

In this paper we show that the growth of InP/GaInAs superlattices with thin (less-than-or-equal-to 3 nm) InP barrier layers is not possible when the surface migration rates of the group III species are large. Large migration rates lead to growth predominantly by lateral motion of steps, due to nucleation at step or kink sites, and therefore to the creation of macro-steps in the InP layer. The planarity of the layers constituting the superlattice is, therefore, lost, with the effect being amplified as the growth proceeds. This effect can be minimized by the use of low growth temperature, high group V flows, high, growth rates, halts after InP growth, a substrate oriented as close to (100) as possible, and by ensuring thickness uniformity across the substrate. The macro-step formation is approximately parallel to [011BAR], implying that either the surface migration rate or the ratio of the lateral growth velocities, v(InPonInGaAs)/v(InPonInP), is maximum along [011]. A similar thickness limitation does not appear to exist for GaInAs, with superlattices containing 1 nm thick GaInAs layers being easily grown. Furthermore, the problems encountered in the growth of InP/GaInAs superlattices were not present in the growth of AlInAs/GaInAs superlattices with similar layer thickness. Finally, it is shown that 100 period (2.5 nm InP/2.5 nm GaInAs) nearly defect free superlattices, with excellent surface morphology, can be grown if the migration rates of the group III species are reduced, substrates oriented close to (100) are used, and thick (40-50 nm) InP layers are introduced every 10 periods.