Island Nucleation in Silicon on Si(111) Growth under Chemical Vapor Deposition

TL;DR

This study investigates the distinct islanding behavior during silicon CVD growth on Si(111), revealing that the presence of two hydrides with different lifetimes explains the unusually high islanding exponent observed experimentally.

Contribution

The paper introduces a modified rate equation theory accounting for two migrating species, providing a better understanding of islanding exponents in CVD growth.

Findings

Large islanding exponent due to two hydrides with different lifetimes

Modified RET explains experimental islanding exponents

Failure of simple island number scaling in two-component systems

Abstract

Recent experiments show that the islanding behavior during chemical vapor deposition (CVD) of Si on Si(111) using disilane (Si${_2}$H${_6}$) is quite different from that due to molecular beam epitaxy (MBE). While the latter can be understood using rate equation theories (RET), the islanding exponent (connecting the power law growth of island density with growth rate) obtained for the CVD growth is a puzzle, with the CVD exponent being almost twice the MBE exponent. We carry out (2+1) dimensional kinetic Monte Carlo(MC) simulations to study this CVD growth. Hydrogen plays a critical role during growth. Disilane breaks up into hydrides on the Si surface. We use MC simulations to explore a number of cases involving one or two migrating species and show that the large islanding exponent is probably due to the presence of two hydrides, one of which has a much shorter lifetime than the other. We modify RET taking this possibility into account in order to shed light on the experimental observation. We calculate the scaling properties of the island distributions using MC simulations and the modified RET, and conclude that the large effective CVD exponents arise from the failure of the simple island number scaling scenario which no longer applies to the two-component situation prevailing under CVD growth conditions.