Chikashi Anayama

CRYSTALLOGRAPHIC ORIENTATION DEPENDENCE OF IMPURITY INCORPORATION INTO III-V COMPOUND SEMICONDUCTORS GROWN BY METALORGANIC VAPOR PHASE EPITAXY

This article presents a comprehensive study of the dependence of impurity incorporation on the crystallographic orientation during metalorganic vapor phase epitaxy of III‐V compound semiconductors. We performed doping experiments for group‐II impurities (Zn and Mg), group‐VI impurities (Se and O), and a group‐IV impurity (Si form SiH4 and Si2H6). The host materials were GaAs, Ga0.5In0.5P, and (Al0.7Ga0.3)0.5In0.5P grown on GaAs substrates. We examined the doping efficiency on the surfaces lying between {100} and {111}A/B. Even though we grew epitaxial layers in a mass‐transport‐limited regime, the doping efficiency significantly depended on the orientation, indicating that the surface kinetics plays an important role in impurity incorporation. Comparing our results with other reports, we found that acceptor impurities residing on the group‐III sublattice and donor impurities residing on the group‐V sublattice, respectively, have their own distinctive orientation dependence. Si donors exhibit orientation d...

Crystal Orientation Dependence of Impurity Dopant Incorporation in MOVPE-grown III-V Materials

Abstract We investigated the crystal orientation dependence of impurity dopant incorporation in III–V compound semiconductors grown be metalorganic vapor phase epitaxy (MOVPE). Doping experiments were performed for group-II acceptors (Zn and Mg), a group-VI donor (Se), and a group-IV donor (Si from silane or disilane) into MOVPE-grown GaAs, Ga 0.5 In 0.5 P, and (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P. The doping efficiency for each impurity was studied between (100) and (111)A/B faces. Comparing our results to previous reports, we found that there is a general rule in the orientation dependence of impurity incorporation, according to dopant groups. The group-II acceptors (Cd, Mg, and Zn), which reside on the group-III sublattice, are preferentially incorporated on the ( h 11)A face ( h ≥ 1) and, in many cases, incorporated less on the ( h 11)B face ( h ≥ 1) than on the (100) face. I n all materials, the Zn incorporation is most prominent on the (311)A face. In contrast, the group-VI donors, which reside on the group-V sublattice, are preferentially incorporated on the ( h 11)B face ( h ≥ 1) and incorporated less on the ( h 11)A face ( h ≥ 1) th an on the (100) face. Comparing to group-II and group-VI impurities, Si generally exhibits weak dependences. Based on rate limiting processes for the dopant incorporation, we constructed a model for the orientation dependence for the group-II and group-VI impurities, considering atomic bonding geometries between adsorbed impurity atoms and adsorption sites.

High‐purity GaSb epitaxial layers grown from Sb‐rich solutions

Undoped GaSb crystals with mirror‐like surfaces were obtained by liquid phase epitaxy from Sb‐rich solutions. The background carrier concentration strongly depended on the growth temperature. By growing crystals below 600 °C, we can obtain a GaSb crystal with a background carrier concentration under 1016 cm−3. Photoluminescence studies showed that native defects related to Sb vacancies were significantly reduced in the GaSb crystal.

Origin of nonradiative recombination centers in AlGaInP grown by metalorganic vapor phase epitaxy

We report the first concrete evidence that oxygen causes nonradiative deep levels in (Alx Ga1–x)0.5In0.5P grown by metalorganic vapor phase epitaxy. We doped AlGaInP with O2 and investigated the oxygen and deep level concentrations by secondary ion mass spectroscopy and isothermal capacitance transient spectroscopy. We confirmed that oxygen causes the D3 (thermal activation energy: ET ≅ 1.0 e V for x = 0.7, nonradiative recombination center) and D2 (ET ≅ 0.46 e V) levels, which we previously found in undoped AlGaInP. We demonstrate that the oxygen and nonradiative deep level concentrations are significantly reduced at higher growth temperatures, higher PH3 partial pressures, and substrate offset from (100) toward [011].

Study on radiative efficiency in AlGaInP/GaInP double-heterostructures : influence of deep level in cladding layers

Abstract We have studied the recombination process of carriers in AlGaInP/GaInP double heterostructures grown by metalorganic vapor phase epitaxy using time-resolved photoluminescence. We found that interfacial recombination is a major process in our samples. We have also studied the influence of the deep-level concentration in AlGaInP-cladding layers on interfacial recombination and found that reducing the deep level concentration from 10 15 to 10 13 cm -3 reduces the interfacial recombination velocity from 140 to 60 cm/s and improves the radiative efficiency. Our results suggest that carriers in the active layer recombine nonradiatively at the interfaces due to the deep level in cladding layers.

Analysis of recombination centers in (AlxGa1−x)0.5In0.5P quaternary alloys

We studied nonradiative recombination centers in undoped (AlxGa1−x)0.5In0.5Pgrown by metalorganic vapor phase epitaxy using transient capacitance spectroscopy. We found three deep energy levels, including a mid‐gap level. We drew an equation to get a capture cross section for minority carriers, and obtained it using isothermal capacitance transient spectroscopy measurement. The mid‐gap level had an electron capture cross section of 2 × 10−10 cm2 and a hole capture cross section of 1 × 10−15 cm2. The time constant of nonradiative recombination through the mid‐gap level was found to be comparable to that of radiative recombination. We concluded that the mid‐gap level is an effective nonradiative recombination center that reduces photoluminescence intensity.

One‐step‐metalorganic‐vapor‐phase‐epitaxy‐grown AlGaInP visible laser using simultaneous impurity doping

We fabricated a GaInP/AlGaInP visible laser with a real‐index guide structure by one‐step metalorganic vapor phase epitaxy using simultaneous impurity doping. We achieved an effective self‐aligned current‐confinement structure in the AlGaInP cladding layer and a threshold current of only 18 mA. The laser had stable transverse‐mode oscillation with a beam astigmatism less than 1 μm.

Liquid phase epitaxial growth of AlxGa1−xSb from Sb-rich solution

Abstract This is, to our knowledge, the first precise report on the liquid phase epitaxial growth of Al x Ga 1− x Sb from a Sb-rich solution. The phase diagram of Al-Ga-Sb at the Sb-rich corner was determined. Epitaxial layers with low background carrier concentration and good surface morphology can be obtained from Sb-rich solutions, when compared to LPE growth from Ga-rich solutions.

Mg-doping transients during metalorgic vapor phase epitaxy of GaAs and AlGaInP

Abstract We studied magnesium-doping transients during metalorgic vapor phase epitaxy of GaAs and (Al x Ga 1- x ) 0.5 In 0.5 P (0 ⪯ x ⪯ 0.7). We examined the transient of Mg concentration depth profile through epitaxial layers when Mg precursors are initially injected into the reactor (doping delay). We found that increasing the Al composition of epitaxial layers, i.e., increasing the mole fraction of Al precursors in the reactor, significantly reduces the Mg-doping delay. We obtained this result for both trimethylaluminum (TMAl) and triethylaluminum (TEAl). We quantitatively modeled this phenomenon based on the competitive adsorption of Mg and Al precursors on the internal surface of the reactor. Our model also explains that the Mg concentration in epitaxial layers increases either linearly or superlinearly with the Mg precursor input, depending on the length of the doping delay.

MOVPE growth and optical properties of AlGaInP/GaInP strained single quantum well structures

Abstract AlGaInP/GaInP strained single quantum well (SSQW) structures have been grown by metalorganic vapor phase epitaxy. 4.2 K photoluminescence (PL) linewidth was as narrow as 9 to 13 meV for a well thickness of 10 nm and the misfit strain over ±1%, indicating excellent structural quality comparable to lattice-matched QWs. The structure of room temperature PL spectra was significantly affected by the misfit strain. Comparison with a theoretical calculation confirmed that the spectra arise from a mixture of optical transitions from the n =1 conduction subband to the n =1 heavy-hole and to the n =1 light-hole subband. The degree of the valence band degeneracy removal could be determined experimentally from the PL spectra.