Y. Horikoshi

GaAs sawtooth superlattice laser emitting at wavelengths λ>0.9 μm

A new type of semiconductor superlattice laser grown by molecular beam epitaxy is realized in GaAs. The active region of the injection laser consists of alternating n and p Dirac-delta doped layers resulting in a sawtooth-shaped conduction-band and valence-band edge. The band gap of this new GaAs superlattice is smaller than the GaAs bulk band gap. Room-temperature operation of broad-area GaAs sawtooth superlattice (STS) injection lasers is demonstrated at a wavelength of 905 nm. The threshold current density of the STS laser is 2.2 kA/sq cm. 10 references.

New long‐wavelength photodetector based on reverse‐biased doping superlattices

A new GaAs photodetector of low capacitance and with high sensitivity in the whole 0.8–1.4‐μm wavelength range has been fabricated from GaAs doping superlattices grown by molecular beam epitaxy. The highly doped yet semi‐insulating superlattice allows application of high reverse bias via selective n+ and p+ electrodes also at room temperature. The excellent photoresponse of the totally depleted device at energies far below the GaAs energy gap arises from the existence of pronounced tail states in the forbidden gap region of the superlattice. Under operating conditions the capacitance of the detector depends only on the electrode geometry and can thus be kept extremely low. This implies high‐speed response of the device.

Low-temperature photoluminescence of MBE-grown GaAs subject to an electric field

Low-temperature photoluminescence of GaAs has been investigated in MBE-grown AlxGa1−xAs-GaAs single heterojunctions subject to an electric field. No peak energy shift is observed in the emission lines due to free excitons and excitons bound to isolated centers when the electric field is applied. In contrast, the excitonic lines arising from the previously described defect-induced bound exciton (DIBX) transitions exhibit a prominent low-energy shift when the electric field is increased. We attribute these lines to excitons bound to acceptor pairs. The excitons bound to distant pairs have smaller binding energies than those bound to closer pairs. They are, therefore, easily dissociated in a weak electric field. The electrons and holes thus dissociated may again be trapped by closer pairs, which results in a low-energy shift of the overall spectrum. The photocurrent measured as a function of the electric field supports Dingles rule for the valence bandedge discontinuity.

GaAs sawtooth superlattice laser emitting at wavelengths greater than 0. 9 micron

A new type of semiconductor superlattice laser grown by molecular beam epitaxy is realized in GaAs. The active region of the injection laser consists of alternating n and p Dirac-delta doped layers resulting in a sawtooth-shaped conduction-band and valence-band edge. The band gap of this new GaAs superlattice is smaller than the GaAs bulk band gap. Room-temperature operation of broad-area GaAs sawtooth superlattice (STS) injection lasers is demonstrated at a wavelength of 905 nm. The threshold current density of the STS laser is 2.2 kA/sq cm. 10 references.

GaAs sawtooth superlattice laser emitting at wavelengths lambda>0. 9. mu. m

A new type of semiconductor superlattice laser grown by molecular beam epitaxy is realized in GaAs. The active region of the injection laser consists of alternating n and p Dirac-delta doped layers resulting in a sawtooth-shaped conduction-band and valence-band edge. The band gap of this new GaAs superlattice is smaller than the GaAs bulk band gap. Room-temperature operation of broad-area GaAs sawtooth superlattice (STS) injection lasers is demonstrated at a wavelength of 905 nm. The threshold current density of the STS laser is 2.2 kA/sq cm. 10 references.