X-ray rocking curves of GaAs/AlGaAs superlattice and GaAs/AlGaAs multiquantum well

Abstract

A majority of the compound semiconductor based electrical and optical devices employ superlattice (SL) or quantum well structures. These structures can be grown either by molecular beam epitaxy or by metal organic vacuum deposition. Compositionally modulated semiconductor superlattice consist of a periodic stack of alternating crystalline layers of high band gap material A and low band gap material B. The typical thickness of a layer is less than or comparable to the de Broglie wavelength of the conduction electron. In cases where the barrier (the high band gap material) thickness is large so that the carriers in the well region (low band gap material) are decoupled from neighboring wells the structure is normally called a multiple quantum well (MQW).
The electrical and optical performance of devices based on these structures (like semiconductor lasers, photodetectors, and transistors) naturally will depend on layer thickness, superlattice period and interfaces sharpness. One method of assessing these parameters is through x-ray diffraction spectroscopy. This method is relatively quick compared to transmission electron microscopy and at the same time is capable of resolving features down to 100 Å. In this study we measure the period and epilayer thickness of GaAs/AlAs SL and GaAs/AlGaAs MQW films. X-ray diffraction rocking curves show satellite peaks and interference fringes (Pendellusong peaks) from which layer thickness and number of periods of the films are extracted.