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(a) Typical structure of a GaAs emitter AlGaAs barrier HEIWIP detector. (b) Band diagram showing the work function for photoemission of carriers. Here, is given by , where and are the contributions from the doping and the Al fraction, respectively. The dashed lines indicate the valence-band edge if the barriers were GaAs.
Band diagram of the hole bands [light hole (LH) and heavy hole (HH)] and an energy diagram illustrating (a) the standard HEIWIP response mechanism and [(b)–(d)] the split-off (SO) band mechanisms. The SO response can be categorized as (b) direct absorption, (c) indirect absorption without scattering, and (d) indirect absorption with scattering. Actions involving the SO band as either the initial or final state are indicated by dashed arrows. The horizontal lines indicate the barrier ( and for the LH/HH and SO holes, respectively) and Fermi energies.
Measured responsivity of HE0204 at various temperatures at . The inset shows the measured absorption for the sample showing the increased absorption from the split-off response. The dashed line shows expected free carrier response as a curve.
Quantum efficiency of detector 1332 at at . The inset shows the calculated absorption coefficient for the free carrier and the SO band absorptions in a -doped GaAs layer.
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