Measurement of Optical Absorption in an Electric Field

Optical absorption by semiconductors and insulators in electric fields has been of interest for several decades. Recently, Franz and Keldysh have independently presented theories which permit an estimation of the magnitude of effects observed. More recently, Callaway developed a more elaborate formulation which permits accurate computation of absorption coefficients. It is the purpose of this work to present the results of an investigation of Callaway's theory. Optical absorption in oriented single crystals of semiinsulating gallium arsenide was investigated over the temperature range 300 to 85°K using non-ohmic contacts and a synchronized pulse-train generator. The Cary 14R recording spectrophotometer was used with a spectral purity between 5 to 9 Å in the IR No. 1 mode of operation. The fields used varied between 1×${10}^4$ and 1×${10}^5$ V/cm.