Toshiaki Fukunaga

Photoluminescence from AlGaAs-GaAs Single Quentum Wells with Growth Interrupted Heterointerfaces Grown by Molecular Beam Epitaxy

Photoluminescence measurements have been carried out for AlGaAs-GaAs single quantum well structures grown by molecular beam epitaxy. At both 77 and 4.2 K a few exciton lines are observed for single quantum wells grown with a few minutes growth interruption at heterointerfaces under As4 pressure. The energy splittings of these peaks well correspond to monolayer well width fluctuations. The full widths at half maximum (FWHM) of these peaks are much narrower than those of peaks obtained from no growth interruption samples. Wide FWHM with no growth interruption sample comes from the small lateral extent of fluctuations comparable to the exciton diameter. Monolayer growth steps are much diminished after a few minutes growth interruption due to the migration of surface atoms.

Reliable operation of strain‐compensated 1.06 μm InGaAs/InGaAsP/GaAs single quantum well lasers

We report the reliable operation of strain‐compensated InGaAs/InGaAsP/GaAs 1.06 μm separate confinement heterostructure single‐quantum‐well laser diodes with tensile‐strained InGaAsP barriers grown on GaAs substrate. High band‐gap strain‐compensation barriers are used to suppress the carrier leakage from a quantum well. This device has a high characteristic temperature of 268 K and low threshold current density of 200 A/cm2 with 0.75 mm cavity length. It was found that the characteristics of lasers without strain‐compensation are worse than those of strain‐compensated lasers at 1.06 μm wavelength. No catastrophic failure in strain‐compensated lasers is observed during 1000 h aging test at 25 °C under an automatic power control of 250 mW while all 1.06 μm lasers without strain‐compensation show catastrophic failure within 1000 h. It suggests that the crystal quality of laser with strain compensation is much better than that without strain compensation. The formation of defects caused by the presence of the...

Ion‐implanted Zn diffusion and impurity‐induced disordering of an AlGaAs superlattice

The diffusion coefficient of ion‐implanted Zn and the Al‐Ga interdiffusion coefficient in an Al0.5Ga0.5As/GaAs superlattice (SL) are extracted from secondary‐ion mass spectroscopy profiles for four diffusion times at 750 °C. The zinc diffusion coefficient goes as the square of the zinc concentration, implying local thermal equilibrium, and is over 200 times smaller than reported values for gaseous‐source Zn diffusions at 650 °C in GaAs. The SL disordering rate increases with increasing zinc concentration and is attributed to the diffusion of positively charged column III interstitials (Ga+mI or Al+mI) with m between 2 and 3.

Photoluminescence from AlGaAs-GaAs single quantum wells grown on variously oriented GaAs substrates by MBE

Abstract Photoluminescence (PL) measurements at low temperatures have been carried out for AlGaAs-GaAs single quantum well (SQW) structures grown on (100), (110), (111)B, (311)A and (311)B GaAs substrates by MBE. A mirror smooth surface was obtained under each optimal growth condition except for (111)B and (110) samples. The (110) surface is cloudy due to the columnar growth. PL results suggest that the height of column is in the order of 10 nm. The film on the (111)B surface consists of a lot of trigonal pyramids, which give a rather broad line width of PL peaks from a SQW compared with the (100) sample. The high optical quality for both (311)A and (311)B SQWs, which is comparable to that for (100) SQWs, is achieved in optimal growth conditions. PL study determines the heavy-hole effective mass of about 0.5 m 0 for the [311] direction.

SIMS Study of Compositional Disordering in Si Ion Implanted AlGaAs?GaAs Superlattice

Compositional disordering in Si ion implanted AlGaAs–GaAs superlattices (SLs) has been studied by SIMS. It is found that Si diffuses fast when the Si concentration exceeds 3×1018 cm-3. The disordering of the SLs always occurs with this fast Si diffusion. It is suggested that the disordering of the SLs is induced by the substitutional exchange of (SiIII–SiV) pairs with the matrix vacancies. The Si diffusion in the SL layer is not enhanced by the presence of the GaAlAs/GaAs interface.

Self‐quasi‐phase‐matched second‐harmonic generation in the proton‐exchanged LiNbO3 optical waveguide with periodically domain‐inverted regions

A self‐quasi‐phase matching technique for second‐harmonic generation (SHG) that uses a proton‐exchanged LiNbO3 optical waveguide with periodically domain‐inverted regions is proposed and demonstrated. The fundamental wave satisfying quasi‐phase‐matching (QPM) condition was generated by an InP/InGaAsP laser diode (LD) with antireflection coated facets which was optically connected to the LiNbO3 waveguide. As the domain‐inverted regions in the optical waveguide act as the distributed Bragg reflector (DBR), the LD is lased by the feedback waves from the DBR. We designed the period of domain‐inverted regions to satisfy the QPM conditions and the high‐reflectance conditions of the fundamental wave. We confirmed that the LD was lased at the wavelength satisfying the QPM conditions and SHG was observed simultaneously.

Electrical and Optical Properties of Si Doped GaAs Grown by Molecular Beam Epitaxy on (311) Substrates

The electrical and optical properties of Si-doped GaAs grown on GaAs (100), (311)A and (311)B substrates by molecular beam epitaxy (MBE) have been studied. A mirror smooth surface is observed for each orientation at low Si atom concentration. Electrical and optical characteristics of the (311)A sample are similar to Si-doped p-type GaAs grown by liquid phase epitaxy, while (311)B samples show almost the same characteristics as (100) samples. Even for a Si atomic concentration up to 1×1020 cm-3, which is too high to keep good surface morphologies of (100) and (311)B samples, excellent morphologies of (311)A samples were obtained. This orientation dependence may be due to different site occupations of Si atoms and surface atom configurations around Si atoms during MBE growth.

Highly Reliable Operation of High-Power InGaAsP/InGaP/AlGaAs 0.8 μm Separate Confinement Heterostructure Lasers

We report the high-power and reliable operation of InGaAsP/InGaP/AlGaAs 0.8 µ m separate confinement heterostructure single-quantum-well laser diodes. High output power of 1.8 W is achieved from an anti-reflection- and high-reflection-coated device with stripe width of 50 µ m and cavity length of 1.25 mm. This device has high characteristic temperature of 164 K and low threshold current density of 300 A/cm2. No catastrophic failure in the laser with 0.75 mm cavity length is observed during 1000 h aging test at 50° C under an automatic power control of 500 mW. The effect of cavity length on laser characteristics is also discussed.

SIMS Study of Si–Be Co-doping Effects for Suppression of Compositional Disordering in AlGaAs–GaAs Superlattices

We have studied the Si–Be co-doping effect for the suppression of the compositional disordering of AlGaAs–GaAs superlattices (SLs) by SIMS. The Si–Be co-doping is found to suppress the fast Si diffusion which is ascribed to the formation of (SiIII–SiV) pairs. The possible mechanism is that the formation of (BeIII–SiIII) pairs prevents that of (SiIII–SiV) pairs. The suppression of the Si fast diffusion impedes the SL disordering. The threshold concentration of Be required to suppress the SL (300 A periodicity) disordering is around 2×1018 cm-3 in the case of 1.5×1019 cm-3 Si concentration.

Implantation Energy Dependence of Composilional Disordering in Si Implanted GaAs/AlGaAs Superlattices Studied by Secondary Jon Mass Speetrometry

Compositional disordering in Si implanted GaAs/AlGaAs superlattices has been studied for various implantation energies by secondary ion mass spectrometry. It is found that at higher energy implantation the disordering is suppressed in the surface region and that the disordering in the deeper region becomes incomplete with the implantation energy. These results are well explained by the formation of damage in the surface region and the reduction of Si concentration, respectively.