Chiaki Domoto

Single-mode optical waveguide fabricated by oxidization of selectively doped titanium porous silicon

Metal-organic compound molecules were selectively doped into the larger pores of a two-layered porous silicon (PS) which had different pore sizes. PS with a graded pore-size distribution was area-selectively formed by utilizing a thin film mask. Titanium-organic compound molecules were doped into the larger pores and the PS was oxidized to form an optical waveguide. Single-mode transmission of 1.55 μm wavelength laser light was successfully observed.

ELECTROLUMINESCENCE IN UNDOPED GAAS/ALAS SUPERLATTICE DUE TO AVALANCHE BREAKDOWN

We have observed electroluminescence (EL) in an undoped GaAs/AlAs superlattice (SL) originating from avalanche breakdown. From EL and photocurrent-voltage characteristics, we found that a large number of electrons were injected into Γ2 states in the SL by avalanche breakdown under a high electric field. The EL spectra revealed two peaks: one having a longer wavelength originated from the radiative recombination process between Γ1 and hh1 states, while the other peak originated from the recombination between Γ2 and hh1 states.

Photoluminescence from high Γ-electron subbands and intersubband electroluminescence using X-Γ carrier injection in a simple GaAs/AlAs superlattice

We report the interband photoluminescence from high Γ-electron subbands and mid-infrared electroluminescence originating from an intersubband transition in a simple GaAs (15.3 nm)/AlAs (4.5 nm) superlattice embedded in a p–i–n structure. Interband photoluminescence properties under applied bias voltages provide conclusive evidence that electrons populate the fourth Γ (Γ4) electron subband in the GaAs layer. This electron population results from the carrier injection into the Γ4 subband from the adjacent X1 subband in the AlAs layer, which is initiated by the X1–Γ4 resonance. We calculate the overlap integral of the envelope functions for Γ-electron and heavy-hole subbands in order to discuss the carrier population in high Γ subbands based on the photoluminescence intensities. The results of analysis suggest that a population inversion can be obtained between the Γ4 and Γ3 subbands under the X1–Γ4 resonant condition. The energy of the intersubband electroluminescence, 100 meV, agrees with the energy spacing between the Γ4 and Γ3 subbands. This demonstrates that the carrier injection into the higher Γ subband using X–Γ scattering will be useful for designing of intersubband-emission devices.