Tsugunori Takanohashi

Photoionization cross section of InP:Fe

The spectral dependence of the photoionization cross section of Fe doped in InP is determined by photocapacitance spectroscopy. The optical process of the carrier emission from the deep acceptor level of Fe is discussed from the results. For the crystal‐field‐split level of Fe2+:5E, the photoionization cross sections for the fundamental transitions of 5E→Γ1 and Γ15→5E are adequately described by the Lucovsky model. Those optical thresholds are 0.63 and 0.78 eV, respectively, at 77 K. In comparison with the deep‐level transient spectroscopy measurements, the following conclusions are obtained. The energy separation between the Fe acceptor level and the conduction‐band edge is constant, but that between the Fe level and the valence‐band edge varies correspondingly to the temperature variation of the InP band‐gap energy. The fact that there is no difference between the optical and thermal activation energies for the 5E→Γ1 transition indicates that the Fe acceptor level is not perturbed by the InP lattice vib...

Fe acceptor level in In1−xGaxAsyP1−y/InP

The Fe acceptor level in In1−xGaxAsyP1−y lattice matched to InP (x=0.47y) is investigated employing current‐voltage characteristics and deep level transient spectroscopy. The activation energy decreases as the proportion of arsenic, y, increases. However, considering the band‐edge discontinuity in this material, it was found that the Fe acceptor level is aligned at a constant energy. This is in excellent agreement with the vacuum referred binding energy model.

Liquid phase epitaxial growth of high purity In1−xGaxAs and InP on (100) and (111)B faces

Abstract The substrate orientation dependence of the impurity concentrations of In1−xGaxAs and InP layers grown from baked solutions was investigated for the (100) and (111)B faces. The carrier concentrations of both In1−xGaxAs and InP can be lowered by baking the growth solutions in a hydrogen atmosphere. The carrier concentration of the ternary and InP layers grown on the (111)B substrates are generally about twice as high as those on the (100) substrates, irrespective of the baking time. By SIMS analysis, S, Si and O were strongly detected in both ternary and InP layers. The impurity concentration for the (111)B oriented ternary layer is higher than that for the (100) oriented layer. The carrier concentration for both faces hardly depends on the growth rate. The carrier concentration depends on the substrate orientation because the distribution coefficient of impurities itself depends on the orientation. Baking the solutions at low temperature is preferable for the growth of high purity layers judging from the results of the evaporation experiments and the SIMS analysis.

SIMS and DLTS Measurements on Fe-Doped InP Epitaxial Layers Grown by MOCVD

SIMS and DLTS measurements have been carried out on Fe-doped InP epitaxial layers grown by metalorganic chemical vapor deposition (MOCVD). Fe was doped with ferrocene Fe(C5H5)2 and smoothly distributed in the epitaxial layers. The solubility limit of Fe is 7×1016 cm-3 at a growth temperature of 650°C. A new electrically active defect was observed in InP doped with the excess concentration of Fe over the solubility limit.

Luminescence characteristics of the (GaP)n(GaAs)n/GaAs atomic layer short-period superlattices

We investigated luminescence characteristics of the (GaP)n(GaAs)n atomic layer superlattices grown on the [001] GaAs substrate by pulsed jet epitaxy. In the single monolayer superlattice (n=1), only direct transition was observed at the whole range of measurement temperature and photoexcitation intensity. Both direct Γ‐type and indirect X‐type emissions were observed in the indirect transition multimonolayer superlattices (n=2–4). These transitions were competitive. The direct emission was stronger at room temperature; however, the indirect emission was intense at low temperatures. This could be explained in terms of oscillator strength and thermal distribution of photoexcitation electrons into the Γ and X levels in the conduction band. Under high excitation, the direct emission increased superlinearly with the excitation intensity, but the indirect emission showed a saturation for its longer radiative recombination lifetime. We also observed the band‐to‐acceptor transition at the lower energy side of the...

Exciton-Transition Energies and Band Structure of (GaP)n(GaAs)n/GaAs Atomic-Layer Superlattices

We studied exciton transitions and the band structure of (GaP)n(GaAs)n/GaAs [001] superlattices for n=1-4, using reflectance and photoluminescence spectral measurements. The exciton-transition energy showed a prominent drop for n=1 by 90 meV for n=2-4. This was attributable to the intensified delocalization of Γ electrons in the GaAs well by tunneling through the extremely thin GaP barrier layers. The transition was defined as direct for n=1, but indirect for n=2-4 by comparing the energies of exciton absorption and photoluminescence emission from the lowest excited state.

Alloy fluctuation effects on the carrier emission from the Fe acceptor doped in liquid‐phase‐epitaxy‐grown In0.49Ga0.51P

We used microscopic model of disordered atomic arrangements to analyze the thermal emission properties of holes from an Fe acceptor doped in liquid‐phase‐epitaxy‐grown In0.49Ga0.51P. The nonexponential properties of hole emission are well explained by the discretely broadened activation‐energy model. The effective width of the broadened level is 90 meV. This communication shows that the activation energy of an Fe acceptor with an arbitrary composition of InGaP can be predicted by the broadening parameter introduced in this study.

Frequency characteristics of the Mn‐doped InP p‐n junction

Admittance spectroscopy is applied to the analysis of the thermal properties of the Mn acceptor‐doped InP grown by liquid‐phase epitaxy. The thermal activation energy and capture cross section are determined as ΔET=183 meV and σp=1.8×10−13 cm2, respectively. The cutoff frequency of the emission of holes from the Mn acceptor is 1 GHz at 300 K. It is shown that the small signal frequency characteristic of a buried heterostructure laser is improved at frequencies f>1 GHz by using the Mn‐doped p‐InP layer for the current blocking region.

Reproducibility of low carrier concentration in LPE InP using batch melts

Abstract A useful and practical method for obtaining n-InP layers with low carrier concentrations by liquid phase epitaxy is presented. This method combines batch preparation of growth melts with compensation of residual donors by the p-type dopant Cd, and needs no long-term baking of the melts. The carrier concentrations could easily be controlled in the range of n = 1.0 x 10 15 -1.0 x 10 16 cm -3 b y varying the amounts of Cd in the batch-prepared melts. Good reproducibility of n = (4.5 ± 1.3) x 10 15 cm -3 has been obtained for 13 growth runs using the same kind of melts. Good uniformity of the carrier concentrations in n-InP layers was found within a wafer and along the growth direction.

Admittance Study of a Single Electron Trap in the LPE InP/InGaAsP Heterostructure Diode

Admittance spectroscopy is applied to the liquid phase epitaxial (LPE) InP/InGaAsP heterostructure diode with a Cd-diffused p+-n junction. A single electron trap is observed in the InP layer. The thermal activation energy is 0.55 eV, and the average capture cross section is 2.7×10-14 cm2 at temperatures 350 K–440 K. The cut-off frequency of the trap is about 30 Hz at room temperature. The trap concentration shows a sudden increase at the InP/InGaAsP heterointerface.