Carbon-doped long wavelength GaAs/Al x Ga1− x As quantum well infrared photodetectors grown by organometallic vapor phase epitaxy

• Published in: Journal of applied physics 1992-04, Vol.71 (7), p.3642-3644
• Main Authors: Hobson, W. S., Zussman, A., Levine, B. F., deJong, J., Geva, M., Luther, L. C.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.350899

We report p-doped long wavelength GaAs/AlxGa1−xAs quantum well infrared photodetectors (QWIP) grown by organometallic vapor phase epitaxy. The operation of these devices is based on the photocurrent induced through valence-band intersubband absorption by holes and, unlike n-doped QWIPs, can utilize normal incidence illumination. Carbon was used as the p-type dopant in a low-pressure (30 Torr) vertical-geometry reactor. The C-doped QWIPs consisted of fifty periods of 54-nm-thick undoped AlxGa1−xAs (x=0.36 or 0.30) and C-doped GaAs wells (Lz=4 or 5 nm). Using normal incidence illumination, the C-doped QWIP with shorter wavelength response (x=0.36, Lz=4 nm) exhibited a quantum efficiency of η=21.4% and a detectivity at the peak wavelength of Dλ=5.4×109 cm √Hz/W at 77 K. The peak and cutoff wavelengths were λp=8.1 μm and λco=8.9 μm, respectively. The C-doped QWIP with longer wavelength response (x=0.30, Lz=5 nm) exhibited a normal incidence η=22.1% and Dλ*=3.5×108 cm √Hz/W for λp=10.5 μm (λco=11.7 μm). The detectivity of the C-doped QWIPs is about four times less than n-doped QWIPs for the same λp but have the advantage of utilizing normal incidence illumination.