MEASUREMENT OF CDXHG1-XTE COMPOSITION DEPTH PROFILES USING AUGER-ELECTRON SPECTROMETRY ON BEVELED SECTIONS

The width of the band gap in the ternary system CdxHg1-xTe (CMT) is a function of the value of x and the assessment of device structures requires reliable techniques for the measurement of x both laterally and with depth. This work describes the development of an Auger electron spectrometry (AES) method for the measurement of CMT composition depth profiles, based on measurement of the Cd/Te ratio along shallow-angle bevelled sections through epitaxial layers, Results are accurate to within 3% relative and the depth resolution (Delta z = 2 sigma) is about 0.04 mu m even through layer structures with a total thickness of about 20 mu m. Techniques for making the bevel sections are described together with the AES measurement and calibration techniques. A composition depth profile is given for a heterostructure grown by metal organic vapour phase epitaxy (MOVPE), showing the interface width (Delta z = 2 sigma) at the composition change to be 0.3 mu m. The CdTe/CMT interface widths in material grown by liquid phase epitaxy (LPE), MOVPE and molecular beam epitaxy (MBE) are shown to be highly dependent on growth temperature, with widths of 1.5, 0.2 and less than or equal to 0.04 mu m respectively.