ELECTRICAL-PROPERTIES OF HGCDTE EPILAYERS DOPED WITH SILVER USING AN AGNO3 SOLUTION

We employed AgNO3 solutions for doping Ag in liquid phase epitaxy (LPE ) grown Hg0.78Cd0.22Te epilayers and found that the minority carrier l ifetimes became longer so that the diode properties improved. After an nealing LPE grown Hg(l-x)Cd(x)Te layers (x = 0.22) in Hg atmosphere, t he epilayers were immersed in an AgNO3 solution at room temperature. T he typical carrier concentration of holes was 3 x 10(16) cm(-3) at 77K . These values were almost the same as for the nondoped wafers. Also, its acceptor level was 3 to 4 meV. This shows that the Ag was activate d. The doped crystals have lifetimes several times longer than those o f the nondoped crystals. Numerical fitting showed the lifetime was lim ited mostly by the Auger 7 process. The Shockley-Read-Hall recombinati on process was not effective. To examine the Ag-doped wafer, we fabric ated photodiodes using standard planar technology. The diodes have an average zero-bias resistance of several Mn and a shunt resistance of a bout 1 G Omega for a 10 mu m cutoff wavelength at 78K. These values ar e about four times higher than those of nondoped diodes. The photo cur rent is also two times higher at the same pixel size. This shows that the quantum efficiency is increased. The extension of the lifetime con tributes to the high resistance and the high quantum efficiency of the photodiode.