Electric, al Properties of HgCdTe Epilayers Doped with Silver Using an AgNO↓(3) Solution

摘要

We employed AgNO↓(3) solutions for doping Ag in liquid phase epitaxy (LPE) grown Hg↓(0.78)Cd↓(0.22)Te epilayers and found that the minority carrier lifetimes became longer so that the diode properties improved. After annealing LPE grown Hg(1-x)Cd(x)Te layers (x = 0.22) in Hg atmosphere, the epilayers were immersed in an AgNO↓(3) solution at room temperature. The typical carrier concentration of holes was 3 × 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 activated. The doped crystals have lifetimes several times longer than those of the nondoped crystals. Numerical fitting showed the lifetime was limited mostly by the Auger 7 process. The Shockley-Read-Hall recombination process was not effective. To examine the Ag-doped wafer, we fabricated photodiodes using standard planar technology. The diodes have an average zero-bias resistance of several MΩ and a shunt resistance of about 1 GΩ for a 10 μm cutoff wavelength at 78IC These values are about four times higher than those of nondoped diodes. The photo current is also two times higher at the same pixel size. This shows that the quantum efficiency is increased. The extension of the lifetime contributes to the high resistance and the high quantum efficiency of the photodiode.