Vacancy-enhanced intermixing in highly strained InGaAs/GaAs multiple quantum well photodetector

Impurity-free vacancy disordering techniques using rapid thermal annealing with electron-beam evaporated SiO2 encapsulant was utilized to study its ef fect on the optical and electrical properties of the highly strained InGaAs /GaAs quantum well infrared photodetector. The photoluminescence peak is bl ueshifted and its line width does not increase much, indicating the composi tional disordering of the quantum well structure and there is no strain rel axation or minimal deterioration of the heterostructure quality. Both trans verse electric and transverse magnetic infrared intersubband transitions ar e retained and observed after intermixing. The absorption peak wavelength i s redshifted from the as grown 10.2 mu m to the interdiffused 10.5 and 11.2 mu m, for 5 and 10 s annealing at 850 degrees C, respectively, without app reciable degradation in absorption strength. Theoretical calculations of th e absorption spectra are in good agreement with the experimental data. Anne aled responsivity spectra of both 0 degrees and 90 degrees polarization are of comparable amplitude but with narrower spectra line width. Dark current of the annealed devices is found to be an order of magnitude larger than t he as-grown one at 77 K. (C) 1999 American Institute of Physics. [S0021-897 9(99)04416-3].