A very long wavelength broadband infrared detector, sensitive over a 10–16 μm spectral range, based on GaAs/AlxGa1−xAs quantum wells grown by molecular beam epitaxy, has been demonstrated. Wavelength broadening of Δλ/λp∼42% is observed to be about a 400% increase compared to a typical bound-to-quasibound quantum well infrared photodetector (QWIP). In this device structure, which is different from typical QWIP device structures, two different gain mechanisms associated with photocurrent electrons and dark current electrons were observed and explained. Even with broader response, D*∼1×1010 cmHz/W at T=55 K is comparable to regular QWIPs with similar cutoff wavelengths.

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A direct conversion technique has been demonstrated to produce highly conductive tracks on silicon carbide by irradiating it with a laser beam. It is found that laser irradiation of insulating silicon carbide substrates decreases its resistivity from 1011 to 10−4 Ω cm. Scanning electron microscopy of laser-irradiated α-silicon carbide substrate reveals dispersed globules on the irradiated track. The atomic force microscopic images of the tracks indicate the conversion of larger structures into smaller, more round-shaped structures suggesting the formation of globules. However, laser irradiation of silicon carbide conductors in the presence of pure oxygen transforms the conducting track into an insulator. The effect of annealing on the electrical properties of the laser-generated conducting tracks is also examined. This technique provides a means of directly writing conducting and insulating tracks on silicon carbide to produce electronic devices for high temperature applications.