Precise thickness measurement within a few monolayers by X-ray diffraction from InGaAs/GaAs strained-layer superlattices

Abstract

We propose a technique to measure the thickness of a GaAs layer with a precision of a few monolayers (MLs) by high-resolution X-ray diffraction (HRXRD) from InGaAs/GaAs strained-layer superlattices (SLSs) on GaAs substrates. Using this technique to monitor the GaAs growth rate, we have successfully controlled the Ga beam flux within ± 1% in molecular beam epitaxy (MBE) growth for continuous 40 runs during four days by increasing the Ga cell temperature to compensate the decrease of the Ga beam flux caused by the consumption of the Ga source. Precise thickness measurements are also demonstrated in the growth on InP substrates by using InAlGaAs/InGaAs SLSs and InAlGaAs/InAlAs SLSs.