Study of semiconductor surfaces and interfaces using electromodulation

• Published in: Surface and interface analysis 2001-10, Vol.31 (10), p.938-953
• Main Author: Pollak, Fred H.
• Format: Article
• Language: English
• Subjects: contactless electroreflectance; devices; photoreflectance; semiconductors
• ISSN: 0142-2421; 1096-9918
• DOI: 10.1002/sia.1131

The modulation spectroscopy technique of electromodulation (EM) is a major tool for the study and characterization of a number of semiconductor surfaces/interfaces and also for the evaluation of process‐induced damage at surfaces. The most useful forms of EM are photoreflectance (PR) and contactless electroreflectance (CER) because they are sensitive to surface/interface electric fields and often yield the sharpest structure (third‐derivative lineshape of the unmodulated spectrum in the case of bulk/thin‐film material). For sufficiently high electric fields the PR/CER spectra may exhibit Franz–Keldysh oscillations, which are a direct measure of the relevant electric field. Furthermore, PR and CER require no special mounting of the sample and hence can be employed in situ (PR) or non‐destructively on wafer‐sized material. This article will discuss some recent applications of PR/CER for the investigation of a number of surfaces/interfaces, such as: process‐induced effects on the surface of Si; Fermi‐level pinning on a number of III–V materials, including low‐temperature‐grown GaAs (with excess As) and wurtzite GaN; Schottky barrier formation; process‐induced damage (sputtering, reactive ion etching, chemically assisted ion beam etching) on III–V materials; homojunctions (GaAs/GaAs); heterojunctions (GaAlAs/GaAs, ZnSe/GaAs, CdTe/GaAs, AlInAs/InP, InGaAs/InP, InGaAs/InAlAs and wurtzite InGaN/GaN); and device structures such as heterojunction bipolar transistors and pseudomorphic high‐electron‐mobility transistors. A number of these studies have been performed in situ with an ultrahigh vacuum environment. Copyright © 2001 John Wiley & Sons, Ltd.