Effect of indium content on the normal-incident photoresponse of InGaAs/GaAs quantum-well infrared photodetectors

Longwavelength InGaAs/GaAs quantum-well infrared photodetectors with indium contents ranging from 25% to 40% have been grown and characterized. Materi al quality has been assessed by photoluminescence and transmission electron microscopy. Intersubband photocurrent, excited by polarized (TE or TM) inf rared light, has been analyzed in order to determine the responsivity for n ormal-incident radiation. It is found that the TE to TM responsivity ratio is lower than 10% in all the samples studied. By changing the indium conten t from 25% to 40%, the increase in the TE to TM photoresponse ratio is as l ow as 3%. Our results are opposite to previous reports of experimental obse rvation of significant TE-polarized light absorption. However, the low effi ciency for normal-incident radiation agrees with various theoretical predic tions. (C) 2001 American Institute of Physics.