Defect Model and Growth Characteristics of Low Temperature GaAs

Abstract

ABSTRACTLow-temperature GaAs layers (LTGaAs) grown by molecular beam epitaxy on GaAs substrates have been characterized by x-ray diffraction techniques. X-ray rocking curve measurements on more than 200 anneal conditions show that through appropriate choice of growth condition, layers with different states of strain are obtained. Three distinct ranges of low temperature growth are defined, labelled as “low-range,” “mid-range,” and “high-range,” corresponding to growth temperatures less than 260 °C, between 260 and 450 °C, and more than 450 °C, respectively. 0.5μm thick films grown in the low-range are amorphous, whereas those in the mid-range are fully strained and lattice-matched to the substrate, and those grown above 450 °C are indistinguishable from ordinary GaAs. Notable properties of mid-range layers are the random behavior of the as-grown strain, and the expansion and contraction of the lattice parameter with thermal anneals up to 900 °C. A growth model for LTGaAs based on arsenic antisite defects is proposed.