Photoluminescence of self-assembled InAs/GaAs quantum dots excited by ultraintensive femtosecond laser Wetting layer states of In As ∕ Ga As self-assembled quantum dot structures: Effect of intermixing and capping layer
We fabricate GaAs-based triangular barrier photodiodes (TBPs), in which type-II GaSb quantum dots (QDs) are embedded in the vertex part of their triangular barriers. Their current–voltage characteristics and photo-responses are studied at low temperatures to show that GaSb QDs enhance the number and lifetime of photo-generated holes that are trapped by QDs in the barrier, resulting in the increase in the electron current around positively charged QDs. An extremely high responsivity of 109 A/W is achieved.
AlGaInAs nanowires or rods of 20-40 nm diameter were formed by depositing an AlGaAs/GaAs/InAs short-period superlattice onto selforganized InAs quantum dots on GaAs. The In content is found to be substantially higher in the rods than in the superlattice matrix, implying that rods serve as favorable paths for electrons. Transport properties measured at 4.2 K on a sample where 79-nm-long rods are buried between n þ -GaAs electrodes show that rods are indeed far more conductive than their matrix barrier. Photoluminescence study has indicated that photogenerated carriers recombine mostly in the seed dot portion of rods. #
InGaAs triangular barrier (TB) structures of various barrier thicknesses have been formed on InP substrates. With them, we have fabricated TB photodiodes that yield a very high responsivity of 2.3 × 104 A/W at 100 K for the 1312 nm light of 320 fW power. By passivating the diode surface with polyimide, the dark current has been markedly reduced. Diodes with thicker barriers show higher sensitivity and responsivity, reflecting the enhancement of the barrier lowering effect by photogenerated holes.
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