InfraredPhysics, 1970. Vol. 10,pp. 125-139. PergamonPress. Printedin Great Britain zyxwvutsrqponmlkjihgfedcbaZY INFRARED TECHNIQUES FOR SEMICONDUCTOR CHARACTERIZATION” J. F. BLACK, E. LANNING and S. PERKOWITZ The Bayside Research Center of General Telephone and Electronics Laboratories Incorporated, Bayside, New York 11360 (Received 2 November 1969) Abstract-The advantages and limitations of optical measurements are discussed and compared with electrical and galvano-magnetic measurements as a routine means of examining the electronic properties of semiconductors. Rapid, accurate, non-destructive optical methods for determining the free charge carrier concentration (N) and mobility (p) in n-type GaAs are described. Measurements of both transmission and reflection over the wavelength range 5-35 pm are shown to be useful for determining N and p in crystals which contain from 5 x 1Ol7 to about 1 x 10ly carriers/cm 3. For carrier concentrations from 5 x 1016/cm3 to 5 x 1018/cm3 transmission measurements from 5 to 14rm were found to be suitable. The optically determined carrier concentration and mobility of polished n-GaAs slices were, in almost all cases, within 30% of the carrier concentration and mobility calculated from Hall effect measurements. A wide variety of crystal shapes and sizes could be evaluated and, with suitable beam condensers and masks, a sampling spot diameter of 1.5 mm was obtained; with the addition of a simple mechanical sample scanning apparatus, inhomogeneity in dopant distribution was easily detected. 1. INTRODUCTION IT has been known for many years that measurements of the optical properties of semi- conductors, especially in the infrared region of the spectrum, could be used to determine the carrier concentration and mobility,(l) electrical properties of great importance to the semiconductor industry. Relatively little has been done, however, to develop routine optical methods of measuring carrier concentration (N) and mobility (P), in spite of the fact that optical techniques can afford high accuracy and sensitivity. The rapid growth of the semiconductor industry has resulted in strong emphasis on measurement techniques that offer simplicity, speed, and versatility. In these elements of performance, optical methods are far superior to electrical methods of measurement. It is, therefore, worthwhile to inquire further into the utility of optical measurements as a routine means of determining free carrier concentration and charge carrier mobility in semiconductors. The advantages and limitations of several different kinds of optical measurements have been considered and they will be discussed and compared with electrical measurements commonly used in semiconductor evaluations. Of principal interest is the quantitative determination of the carrier concentration and mobility; these quantitative measurements may be averages over a relatively large region of a semiconductor crystal, or values representative of a well-defined and pre-selected small region of the crystal. Of secondary interest, but perhaps of more importance ultimately, is the determination of homogeneity * Parts of this paper were presented at the meeting of the Electrochemical Society, 4-9 May 1969 in New York. 125 2D