Electromodulation of semiconductors and semiconductor microstructures utilizing a new contactless technique

We present results of a new contactless mode of electroreflectance (ER) which utilizes a condenser-like system. One electrode consists of a transparent conductive coating on a transparent substrate which is separated from the sample surface by a thin layer of air. We have measured the contactless ER (CER) spectra from a number of materials including semi- insulating bulk GaAs; epitaxial In0.15Ga0.85As; bulk Hg0.8Cd0.2Te (80 K and 300 K), a GaAs structure with a large, uniform electric field; and a GaAs/Ga1-xAlxAs (x approximately equals 0.2) coupled double quantum well. Some measurements were performed up to 500 K. The phase of the CER signal yields information about the nature of the band bending at the surface of bulk or epitaxial material. The relative merits of CER and photoreflectance are discussed.