Soon Jae Yu

Study of Ga ion implantation damage and annealing effect in Sn‐doped InP using Raman scattering

The damage of Sn‐doped InP by Ga ion implantation with fluences ranging from 1×1013 to 5×1014 cm−2 and annealing effects (150–650 °C) are investigated by means of Raman scattering. The shift and asymmetrical broadening of a longitudinal optical phonon peak and the appearance of transverse optical mode and disorder‐activated acoustic modes show that the damage effect by Ga ion implantation is very large, and the crystalline structure becomes amorphouslike at a fluence as low as 1×1014 cm−2. The damaged state is investigated in terms of the spatial correlation model and quantitatively estimated by comparing the Raman peaks for longitudinal optical and transverse acoustic phonon modes with the theoretical calculations. It is shown that the correlation lengths at 1×1013 cm−2 are 36 and 29 A, respectively. This largely damaged structure is found to be recovered by annealing at as low as 250 °C.

Gas source molecular beam epitaxy growth of short period GaP/AlP(001) superlattices

Short period GaP/AlP superlattices are grown on GaP and GaAs substrates at 600 °C by gas source molecular beam epitaxy with growth interruption. Alternating monolayer growth of GaP and AlP is confirmed by the observation of the reflection high‐energy electron diffraction intensity oscillations during growth. The formation of short period superlattice structures and the zone‐folded LO phonons are observed in the x‐ray diffraction rocking curves and Raman spectra, respectively.

RAMAN SCATTERING STUDY OF THERMAL INTERDIFFUSION IN INGAAS/INP SUPERLATTICE STRUCTURES

Interdiffusion process of InGaAs/InP superlattice structures by thermal annealing of 700–850 °C is studied by Raman spectroscopy. Peak intensities and peak energies of InAs‐, GaAs‐, and InP‐like longitudinal optical (LO) phonon modes change with thermal annealing temperature and time. Depth profiles of the group III and group V atoms are estimated quantitatively by measuring the variations of the peak energies of the LO phonon modes and the ratios of the mode intensities. The energy shift of the GaAs‐like LO peak showing a small broadening, the existence of nonenergy shift InP LO phonon peak and the emerging of InP‐like LO peak in the lower energy region indicate that the interdiffused superlattice consists of uniform compositional InGaAsP well and InP barrier layers and sharp interfaces. It is found that the resulting InGaAsP quaternary alloy is roughly lattice‐matched to InP (<±0.5%). It is also found that the diffusion coefficient in the well region is larger than that in the barrier region, and that t...

Gas source MEE (migration enhanced epitaxy) growth of InP

Abstract High-quality InP layers are grown by gas source MEE (migration enhanced epitaxy) method at 350°C. It is found that even at a substrate temperature as low as 350°C, the desorption of some amount of phosphorus from the InP surface occurs when the PH 3 flow is interrupted, although the RHEED pattern is still showing the (2×4) reconstructions. As a result, the perfectly alternating supply of indium and phosphorus can be achieved only when PH 3 is supplied with a proper interruption time before the supply of In. It is also found that InP layers grown by gas source MEE at 350°C have optical properties equal to or better than those grown by conventional gas source MBE (molecular beam epitaxy) at 470°C.

Influence of hydrogen on the step flow growth of GaAs on vicinal surfaces by gas‐source migration enhanced epitaxy

Step flow growth of GaAs on the vicinal surfaces by gas‐source migration enhanced epitaxy (MEE), the combination of gas‐source molecular beam epitaxy and MEE, is studied with the reflection high‐energy electron diffraction (RHEED) intensity oscillation. It is found that the use of the thermally cracked AsH3 instead of solid As (As4) as an As source enhances step flow growth of GaAs on the (001) surface misoriented toward the [110] direction. The same tendency is also observed in the MEE growth using As4 under the hydrogen supply. It is considered that the enhancement of step flow growth in the gas‐source MEE is caused by the hydrogen atoms terminated at the steps.

InGaAsP/InP quantum wires fabricated by focused Ga ion beam implantation

InGaAsP/InP quantum-wire structures are fabricated by focused Ga ion beam implantation onto InGaAs/InP single quantum well (QW) structures. It is found that InGaAsP layers produced by the intermixing of InGaAs/InP QWs by Ga ion implantation and subsequent thermal annealing are nearly lattice matched to the InP substrate. Fabricated quantum-wire structures exhibit photoluminescence spectra showing a large blue shift, which is induced by the carrier confinement into wire structures and the change of well composition.

Formation of a High-Electrical-Resistance Region in InP by Ga Ion Implantation

A high-electrical-resistance region as high as 1×104 Ωcm can be formed in Si-doped InP (n=1×1018 cm-3) layers by 8×1014 cm-2 Ga focused ion beam (FIB) implantation and 500–600°C annealing. The clear photoresponse is also observed in the Ga-FIB-implanted diode structures after annealing. A drastic carrier concentration decrease and the existence of residual defects are confirmed by Raman scattering measurement.

Photoluminescence from InGaAs/InGaAsP quantum wires fabricated by Ga focused ion beam

Fabrication of InGaAs/InP quantum wires was tried by Ga focused ion beam implantation. (AIP)

Microscopic Mechanism of Electrical Noise in Co/Si Thin Film Structures

A microscopic mechanism of the production of electrical fluctuations in noncrystalline structures has been studied by measuring 1/f noise parameters and analyzing microstructure of Co/Si interfaces along the silicide nucleation reaction path. The measured noise power spectral density presents the largest fluctuations near the structural (noncrystalline-to-crystalline) transition and the electronic (semiconducting-to-metallic) transition region. The amplitude of the noise spectral density at the frequency of 1 Hz drops more than 3 orders after the nucleation of the first cobalt silicide phase. The variation of the noise parameter is assumed to be an indication of the phase transformation along the nucleation reaction path in a Co/Si thin film system. Structural studies suggest that the observed electrical noise might originate from cobalt atom movements in reversible processes between different chemical structures.