Strain compensated In1-xGaxAs(x<0.47) quantum well photodiodes for extended wavelength operation

The use of highly strained (-2.0%) In0.83Ga0.17As quantum wells for the detection of light to a wavelength of lambda similar to 2.0 mu m is reported. Crystal quality for a 50 period multiple quantum well (MQW) detector grown on InP substrates is maintained through strain compensation using tensile strained In0.83Ga0.17P barriers. Transmission electron microscopy and double crystal x-ray diffraction reveal smooth interfaces and no observable defects for In0.83Ga0.17As layers with widths less than 80 Angstrom. Single-pass quantum efficiencies of 30% have been achieved at lambda=1.95 mu m, using a 75 mu m diam MQW, strain-compensated, top illuminated, low dark current (similar to 250 pA at 20 V) p-i-n detector. The theoretical cutoff wavelength limit for diodes fabricated using this technique is calculated to be lambda=2.15 mu m. (C) 1998 American Institute of Physics. [S0003-6951(98)00542-7].