Investigation on gold and aluminum contacts for Cd_0.8Mn _0.2Te crystals

We report measurements on the nature of gold (Au) and aluminum (Al) contacts with Cd_1-xMn_xTe (x = 0.2, CdMnTe) crystals grown by the vertical Bridgman method. Metal contacts were deposited on CdMnTe wafers through electroless Au, sputtered Au and evaporated Al. Current-voltage characterizations show that the as-deposited Au contacts are ohmic, while the as-deposited Al contacts are rectifying. The electroless Au contact is found to yield a more ohmic contact than the sputtered Au. The interfaces between Au and CdMnTe are studied by x-ray photoelectron spectroscopy (XPS), which shows that electroless Au is injected more into a CdMnTe sample than sputtered Au. Hall measurements reveal that the as-grown CdMnTe is of p-type conductivity, with a carrier concentration of (5 ± 1) × 10¹² cm^-3 and Hall mobility of 60 ± 5 cm² V^-1 s. The Schottky barrier height between Al and CdMnTe is measured by current-voltage (I-V) and capacitance-voltage (C-V) measurements, which reveal that the barrier heights are 0.793 0.005 eV and 0.878 ± 0.002 eV, respectively. The Norde method is also used in order to extract the barrier height of the Al contact with CdMnTe and the value is found to be 0.813 ± 0.002 eV, which is in agreement with that obtained by the I-V method.