The dark current as a function of temperature and infrared absorption of thep-dopedIn0.15Ga0.85As/Al0.45Ga0.55Asmultiple quantum well structures grown by molecular beam epitaxy are investigated. The dark currentIdof the structure is found to be basically symmetrical over a voltage range from −10 to +10 V. It is about10−9 Aat a bias of 1 V at 80 K, more than two orders of magnitude lower than that reported forp-doped GaAs/AlGaAs QW structures with the same size. It is also found thatIdis proportional toT exp[−(EC–EF)/kT]at 70 K and above while at temperatures below 30 K it does not change significantly. TheEC–EFdecreases with the increase in bias in an exponential form, due likely to energy bandgap bending. A strong infrared absorption peaked at a wavelength of 10.7 &mgr;m is in excellent agreement with the estimated value of 10.4 &mgr;m. ©1998 American Institute of Physics.