Influence of trench depth on the misfit dislocation density at strained epitaxial layer interfaces grown on patterned GaAs substrates

Abstract

The number of misfit dislocations in strained, epitaxial InGaAs layers can be significantly reduced by growing on patterned substrates. Etched trenches on these substrates block misfit dislocation propagation from mesa to mesa. To determine the minimum trench depth needed to block misfit dislocations, 200 μm×200 μm mesas separated by 10‐μm‐wide trenches of varying depths were etched into a GaAs substrate before organometallic chemical vapor deposition of 300 or 600 nm In_0.04Ga_0.96As strained layers (several times the critical thickness). Three isolation regimes are seen in the 300‐nm‐thick InGaAs samples. The shallowest trenches, regime I, below 300 nm, do not completely block all dislocations. Misfit dislocations are blocked by trenches 300–500 nm deep, regime II, after they glide down the mesa walls and stop at the far side of the trenches. Trenches greater than 500 nm, regime III, stop dislocations at the mesa edges. The 600‐nm‐thick InGaAs layers with trench depths greater than 450 nm completely stopped all misfit dislocations. The third regime did not occur for trenches as deep as 650 nm. These results show that the epitaxial layer does not have to be discontinuous to prevent misfit dislocations from gliding across patterned substrates.