Front surface control of Cr redistribution and formation of stable Cr depletion channels in GaAs

A technique has been investigated for creating sharply defined (near‐surface) ’’square‐well’’ Cr‐depletion channels in GaAs with subsequent stability of Cr to anneal temperatures of 850 °C. Using 100‐keV B+ implants into surface‐ionized GaAs, followed by annealing (capless) at temperatures <800 °C in arsine, we observed depletion of Cr across the B‐ implantation profile from levels of ≃1017 to ≃3×1015 atoms/cm3. A flat depletion channel is formed, defined by a relatively abrupt shoulder and a maximum channel width of ≃1 mm. Hall effect and C‐V profiles showed n‐type conduction across the channel and Hall mobilities of ≃5200 and ≃11 600 cm2/V sec at 300 and 77 ° K, respectively. Measured carrier concentrations were in agreement with secondary‐ion mass spectroscopy measurements of bulk donor impurity levels.