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 req uires reliable techniques for the measurement of x both laterally and with depth. This work describes the development of an Auger electron s pectrometry (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 wi thin 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 abo ut 20 mu m. Techniques for making the bevel sections are described tog ether with the AES measurement and calibration techniques. A compositi on 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 interf ace widths in material grown by liquid phase epitaxy (LPE), MOVPE and molecular beam epitaxy (MBE) are shown to be highly dependent on growt h temperature, with widths of 1.5, 0.2 and less than or equal to 0.04 mu m respectively.