Growth and characterization of a bound-to-quasi-continuum QWIP with Al-graded triangular confinement barriers

A bound-to-quasi-continuum GaAs-AlGaAs quantum-well infrared photodetector (QWIP) with absorption peak centered at 9 μm has been grown and characterized. Instead of the abrupt interfaces between AlGaAs layers, a different configuration based on AlGaAs graded triangular barriers is used in this work. This structure allows one to grow all the layers with one single Al cell avoiding growth interruption. The detectors show symmetric behavior in the current versus voltage characteristic. Peak responsivities as high as 0.5 A/W using a tilted substrate holder and without any light coupling mechanism were measured. Besides, photocurrent response in normal incidence, without diffraction grating, was also observed.