Structural and electrical properties of CdTe layers grown on ZnTe/GaAs by hydrogen transport VPE

The structural and electrical characterisation of CdTe epilayers grown by H -2 transport vapour phase epitaxy (H-2 T-VPE) on ZnTe/(100)GaAs is reported . Double-crystal X-ray diffraction measurements indicate the material high crystalline quality, leading to (4 0 0) peak FWHM of 59 arcsec for similar to 30 mu m thick epilayers. CdTe grown at temperatures T-D < 650 degrees C are p-type, but turn to n-type for T-D > 650 degrees C, For 650 degrees C < T-D < 700 degrees C, room-temperature (RT) resistivity in the 10(5)-10(6) Ohm cm range is obtained. Nail measurements performed on n-type samples of different thicknesses grown at T-D = 764 degrees C show RT carrier concentr ations in the 10(14)-10(11) cm(-3) range. For a 22 mu m thick epilayer two donor states are found: the most abundant one almost compensates a 10(18)cm (-3) density of accepters; the second donor, having an ionisation energy E- D = 0.186eV, determines the sample n-type properties, its concentration bei ng similar to 10(15) cm(-3) A compensation ratio K greater than or equal to 0.9997 holds for this epilayer. It is suggested that Ga diffusing from GaA s into CdTe gives rise to the above donor states. (C) 2000 Elsevier Science B.V. All rights reserved.