Resonant-cavity infrared optoelectronic devices |
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Authors: | J L Pautrat E Hadji J Bleuse N Magnea |
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Affiliation: | (1) Departement de Recherche Fondamentale sur la Matiére Condensèe, SP2M/PSC, CEA-Grenoble, 17 rue des Martyrs-F 38054 Grenoble, Cedex 9, France |
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Abstract: | The CdxHg1−xTe compounds are well suited to the design of resonant microcavity devices. Indeed these compounds display a wide variation
of bandgap and refractive index with composition, while the lattice parameter remains practically unchanged. Microcavities
resonating in the 3–5 μm range have been prepared by molecular beam epitaxy. Light emitting diodes (LEDs) are obtained by
stacking a lower Bragg mirror (10.5 periods) which is doped n-type and a nominally undoped cavity medium containing a 50 nm
active layer (CdTe-HgTe pseudo-alloy). The upper mirror is a gold layer deposited on the cavity, which is partly p-type doped.
The diode emission is observed under direct bias, up to room temperature, in coincidence with the cavity resonance mode (linewidth
8 meV). It is much narrower than the inhomogeneous linewidth of the active layer (60 meV at 300K). The directivity is also
much better. The diode properties are only very slightly dependent on temperature. A similar device can also be designed to
make an infrared detector whose active layer thickness is reduced with respect to conventional detectors. The detector efficiency
at the resonance wavelength may be increased by a factor close to the cavity finesse. With 16.5 periods in the lower mirror
and a dielectric mirror as upper mirror (seven periods of ZnS/YF3), it has been possible to make a cavity resonating at 3.06 μm whose quality factor reaches 350. By photopumping the cavity
across the dielectric mirror with a YAG microlaser, a laser emission occurred at the cavity resonance. At 10K, the laser threshold
is 45 kW/cm2 and the linewidth is only 1.7 meV. These results demonstrate the usefulness of the microcavity concept for designing new
devices such as LED or lasers which could be the basis for new applications of CdHgTe compounds. |
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Keywords: | HgCdTe infrared optoelectronic devices molecular beam epitaxy resonant cavity |
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