Junji Komeno

Atomic Structure of Ordered InGaP Crystals Grown on (001)GaAs Substrates by Metalorganic Chemical Vapor Deposition

InGaP crystals grown on (001)GaAs substrates by metalorganic chemical vapor deposition are structurally evaluated by transmission electron microscopy. High-resolution electron microscopy observation and electron diffraction analysis of both the (110) and the (10) cross-section specimens strongly suggest that ordering of column III atoms on only two sets of the (111) planes with doubling in periodicity of (111) layers, i.e., In/Ga/In/Ga/In/Ga. . ., is occurring in the crystal. The ordering of the crystal is not perfect, and the ordered regions are assumed to be plate-like microdomains.

Transmission electron microscopic observation of InGaP crystals grown on (001)GaAs substrates by metalorganic chemical vapor deposition

Abstract The detailed nature of ordered structures and the effect of rotation of the substrates on their formation are studied by transmission electron microscopy, for the first time, in InGaP crystals grown on (001)GaAs subtrates by atmospheric metalorganic chemical vapor deposition. In InGaP crystals grown with substrate rotation, ordering occurs in column III atoms on only one of the four equivalent (111) planes with doubling in periodicity of (111) layers, i.e. … In/Ga/In/Ga/In/Ga/…. The ordering of the crystals is not perfect, and the ordered regions are found to be plate-like micro-domains lying on nearly the (001) plane. On the other hand, without rotation of the substrate, ordering occurs on two equivalent (111) planes and the size of the ordered domains becomes larger with a drastic increase of relative volume of the ordered regions. Independent of substrate rotation, modulated structures are observed in two equivalent 〈100〉 directions.

Pseudomorphic n-InGaP/InGaAs/GaAs grown by MOVPE for HEMT LSIs

InGaP/InGaAs/GaAs heterostructures were grown by atmospheric pressure MOVPE. Excellent uniformity was obtained for doping concentration, thickness, and composition of the epitaxial layers by rotating the substrate and cooling the inner tube. The optimum gas switching sequence for achieving sufficient mobility and sheet carrier concentration was found. Enhancement-mode and depletion-mode HEMTs were fabricated using the very thin InGaP layer as an etching stopper layer. These are essential for the fabrication of HEMT LSI circuits. The discrete devices do not exhibit I–V collapse at low temperature. Short channel effects are negligible for gate lengths as small as 0.15 μm, owing to good carrier confinement in the pseudomorphic quantum well channel and a high aspect ratio under the thin n-InGaP layer. These advantages make InGaP/InGaAs/GaAs heterostructures well suited to HEMT LSIs applications.

The growth of GaAs, AlGaAs, and selectively doped AlGaAs/GaAs heterostructures by metalorganic vapor phase epitaxy using tertiarybutylarsine

The prevention of disastrous leakage of AsH3 is a requirement for metalorganic vapor phase epitaxy systems. Less hazardous organoarsine has been investigated as an alternative to AsH3 , and recently, tertiarybutylarsine (tBAs) has been used as an arsenic source. So far the use of tBAs has been restricted to fundamental experiments. The growth of GaAs, AlGaAs, and selectively doped AlGaAs/GaAs heterostructures has been studied using tBAs and AsH3, and the properties of the epilayers grown using both sources have been compared. From the PL spectra at 4.2 K, it was determined that GaAs films using tBAs were of high purity and equivalent to those using AsH3. The properties of AlGaAs grown using tBAs are as good as those using AsH3. A higher V/III ratio results in high‐quality AlGaAs layers. The epitaxial uniformity of growth rate and AlAs mole fraction along a wafer using tBAs was poorer than those using AsH3 due to vapor phase reactions in the trimethylgallium‐tBAs mixture. However, the increase of total gas...

Photoionization of deep traps in AlGaAs/GaAs quantum wells

We investigated photoionization of deep traps in AlGaAs/GaAs multiple‐quantum‐well layers and measured the photocurrent (PC) parallel to the layers under a small electric field. There is a small shoulder due to the photoionization of a deep trap on the low‐energy side of the n=1 exciton resonance peak in the PC spectra taken as a function of the excitation energy ℏω. The excitation energy dependence f(ℏω) and amplitude A of the photoionization cross section, σ(ℏω)=Af(ℏω), are determined by the time constants of single‐shot PC transients. The excitation energy dependence increases linearly with excitation energy. The photoionization threshold energy EMQWth and the amplitude A increase as well thickness decreases. These characteristics are explained well by our theoretical study on the photoionization of a deep trap to subbands.

Metalorganic vapor phase epitaxy using organic group V precursors

Abstract Metalorganic vapor phase epitaxy (MOVPE) using organic group V precursors is described. The direct-feed control method for organic group V precursors enables the stable transport of large quantities of group V sources to a reduced-pressure barrel reactor capable of growing multiple wafers in a run. Heterostructures grown using tertiarybutylphosphine (TBP) and tertiarybutylarsine (TBAs) were of high quality and extremely uniform. Trial fabrications of multi quantum well (MQW) lasers, low-noise amplifiers, and prescaler integrated circuits (ICs) resulted in excellent device characteristics.

Semi‐insulator‐embedded InGaAsP/InP flat‐surface buried heterostructure laser

A new structure semi‐insulator‐embedded flat‐surface buried heterostructure 1.3 μm InGaAsP/InP laser has been developed using chloride vapor phase epitaxy. cw threshold currents as low as 18 mA and high‐temperature cw operation up to 100 °C have been obtained. Small‐signal response above 4 GHz has been achieved and no remarkable roll‐off has been observed, which is due to small parasitic capacitance.

Differences in Si doping efficiency in tertiarybutylarsine, monoethylarsine and arsine for GaAs and AlGaAs grown by MOVPE

We investigate differences in Si doping of GaAs and AIGaAs between group-V sources. Si2H6 and SiH4 doping dependence on growth temperature, V/III ratio, total flow rate, growth rate, and off angle of substrate orientation was examined using tertiarybu-tylarsine (TBAs), monoethylarsine (EtAs), and arsine with a horizontal atmospheric pressure reactor. With either dopant source, Si incorporation for films grown using TBAs or EtAs was always higher than that using arsine. Using silane, dependence of Si incorporation on growth temperature and total gas flow velocity is different between group-V sources. Using disilane, dependence on V/III ratio and total gas flow velocity is different between group-V sources. These results imply that gas phase reactions play an important role. From the kinetic simulation of the decomposition of group-V sources, we verified that the concentrations of AsH3, AsH2, and AsH in vapor near the substrate are quite different among group-V sources. AsH2 is dominant reactant when using TBAs. We propose that H2AsSiH3 (silylarsine) is formed by the reaction between AsH2 radical and SiH4 and silylarsine should contribute Si incorporation reactions, resulting in high Si incorporation efficiency with TBAs and EtAs. We also suggest that AsH3 inhibits Si incorporation.

Effects of the growth conditions on the incorporation of deep levels in vapor‐grown GaAs

The effects of various conditions on the incorporation of deep levels in VPE GaAs were studied by capacitance spectroscopy. Three kinds of electron traps (Ec−0.86 eV, Ec−0.84 eV, and Ec−0.77 eV) and two kinds of hole traps (EV+0.60 eV and EV+0.44 eV) were measured. Trap concentrations increased strongly with increasing growth rate, but were found to be independent of n‐doping level, type of dopants used (S, Se, Si, Ge, Sn), and growth atmosphere (H2 or N2). These experimental results indicate that the centers responsible for these levels are not due to simple substitutional chemical impurities, but are related to native defects or to complexes involving native defects.

Selective growth of InP buried structure by chloride vapor phase epitaxy

Selective growth of an InP buried layer by In/PCl3/H2 vapor phase epitaxy was developed for buried layer GaInAsP/InP long wavelength laser diodes. For the first time, a completely flat‐surface buried layer was grown into grooves with good morphology on a (100) exactly oriented InP substrate, but not on a (100) 2° off oriented substrate. We found that the side of the groove was covered with a buried InP layer in the early stage of epitaxial growth. Therefore, the present selective growth would be effective for the protection of the interface between the active and buried layers from thermal degradation. The resistivity of InP, measured by using an n‐i‐n structure, was found to be higher than 103 Ω cm at room temperature, which is sufficient for the buried layer of an usual laser diode.