A NORMAL-INCIDENCE TYPE-II QUANTUM-WELL INFRARED PHOTODETECTOR USING AN INDIRECT ALAS AL0.5GA0.5AS SYSTEM GROWN ON (110) GAAS FOR MIDWAVELENGTH AND LONG-WAVELENGTH MULTICOLOR DETECTION

A normal-incidence type-II indirect AlAs/Al0.5GaD.5As quantum-well inf rared photodetector grown on (110) GaAs by molecular-beam epitaxy for mid- and long-wavelength multispectrum detection has been developed. T he normal-incident excitation of long-wavelength intersubband transiti on was achieved in the [110] X-band-confined AlAs quantum wells. Six a bsorption peaks including four from X-band to r-band intersubband reso nant transitions were observed at wavelengths, lambda(p1 - 6) = 2.2, 2 .7, 3.5, 4.8, 6.5, and 12.5 mum. The resonant transport from X band to GAMMA band gives rise to high photoconductive gain, which is highly d esirable for focal plane arrays image sensor applications.