Determination of the residual carbon acceptor concentration in semi-insulating GaAs wafers by IR spectroscopy: accuracy and detection limits

The IR absorption method is investigated in detail with respect to a routine application in semiconductor industry laboratories. The experimental and analytical procedures necessary for an accurate determination of the residual carbon acceptor (C As ) concentration also in commercial wafers are given. A specific technique to eliminate the interference fringes arising from multiple reflections inside the wafer is presented. At a measurement temperature of 77 K the detection limit for carbon is 6*10 13 cm -3 in wafers of 5 mm thickness. The IR method is also applicable to commercial wafers giving a detection limit of about 6*10 14 cm -3 .