Kazuo Mizuguchi

MOCVD GaAs growth on Ge (100) and Si (100) substrates

Abstract GaAs epitaxial layers are grown on exact (100) and slightly off-oriented (100) Ge and Si substrates by MOCVD. The etched patterns with molten KOH of the GaAs layers on exact (100) Ge and Si substrates show antiphase domain structure, but those on 2° off (100) toward [011] Ge and Si substrates reveal single domain. The single domain is supposed to arise from “phaselocking steps” existing on the surface of 2° off (100) Ge and Si substrates. These GaAs layers are characterized by X-ray rocking curves and 4 K photoluminescence spectra.

Reduction of Dislocation Density in GaAs/Si by Strained-Layer Superlattice of InxGa1-xAs-GaAsyP1-y

Dislocation density in GaAs layers grown on Si substrates has been investigated by measuring in-depth profile of the etch pit density (EPD) using a molten KOH. Reduction of EPD into 107 cm-2 level for the layer of 2-3 µm thickness is attained by the post annealing at 900°C for 30 min. Further reduction of dislocation has been achieved using InxGa1-xAs-GaAsyP1-y strained-layer superlattices (SLSs); step-like reduction of the dislocation at the SLSs and its continuous decrease even passing through the SLSs have been observed.

Improvement of InP crystal quality grown on GaAs substrates and device applications

We have investigated the effect of strained-layer superlattice (SLS) buffer layers on the crystal quality of InP grown on GaAs substrates. The various SLSs such as In0.63Ga0.37As/InP, In0.73Ga0.27As/InP, In0.9Ga0.1P/InP, and GaAs/InP were tested. It is found that the optical property of InP layers grown on In0.63Ga0.37As/InP SLSs was dramatically improved. An InGaAsP/InP double heterostructure laser diode and an InGaAs PIN photodiode (PD) on InP/GaAs with an In0.63Ga0.37As/InP SLS have been fabricated. The CW threshold current of the laser at room temperature was as low as 31 mA, and the dark current of the PD was 30 nA at - 10 V.

Improvement of InP Crystal Quality on GaAs Substrates by Thermal Cyclic Annealing

We have studied the effect of thermal cyclic annealing (TCA) on the crystal quality improvement of MOCVD grown InP on GaAs substrates. The crystal quality has been evaluated by the etch pit density (EPD), X-ray diffraction and photoluminescence (PL) measurement. It is found that the TCA is effective in reducing the dislocation density, and that the annealing at 700°C is essential to confine the point defects near the InP/GaAs interface. The EPD is reduced from 6×107 cm-2 to 3×107 cm-2, and the defect-related PL peak intensity is decreased below the residual level in the 5 µm-thick InP on GaAs.

The Multiple Quantum Barrier Structures and their Application to the High Power Visible Laser Diode with the Strained InGaP Active Layer Grown by MOCVD

Abstract We introduced a multiple quantum barrier (MQB) which was grown by MOCVD between the active layer and p-cladding layer to enhance potential barrier height. The MOCVD system was improved to realize the growth of MQB structures for the first time. We compared threshold current densities (Jth) of various barrier/well thickness combinations in order to optimize the MQB structure. We found that the thickness of barriers and wells should be 1.7 and 1.15 nm, respectively, to minimize Jth. The optimized MQB significantly reduced the Jth of visible laser diodes. Strained active layers with compressive stress were employed as another approach for the improvement of the threshold current. We found that the strained active layer is as effective as the MQB in reducing Jth. The lowest Jth has been achieved by the combination of MQBs and strained active layers. We realized an output power of 40 mW, at 90°C, at a lasing wavelength of 675 nm. to our knowledge, these are the best data.

Highly uniform growth of GaAs and AlGaAs by large-capacity MOCVD reactor

Abstract Highly uniform growth of GaAs and AlGaAs epitaxial wafers has been carried out by a large-capacity MOCVD (metalorganic chemical vapor deposition) reactor. The physical and electrical properties of the epitaxial layers depend on the carrier gas H2 flow rate. The uniformity of growth rate along the gas flow direction is explained by the stagnant layer model. The variation of growth rate along the gas flow direction within two 2 inch diameter wafers is ⩽ 5% under the optimized carrier gas H2 flow condition for GaAs and AlGaAs growth. The variation among twenty 2 inch diameter wafers is ⩽ 8%. The variation of Al composition of AlGaAs is ⩽ 1% along the gas flow direction and among ten 2 inch diameter wafers.

Extremely low threshold InGaAsP/InP DFB laser by MOCVD/LPE hybrid process

Abstract The InP and InGaAsP layers grown by low pressure MOCVD were characterized by a double crystal X-ray diffractometry and 4.2 K photoluminescence measurements. It was confirmed that these layers were of high quality and the hetero-interfaces were very sharp. The growth characteristics on corrugated substrates were investigated for the application to 1.3 μm InGaAsP/InP distributed feedback (DFB) laser diodes. These devices exhibited extremely low threshold currents of 3.8 mA in CW mode at 20 ° C for a normal cavity length of 300 μm. The typical values of the differential efficiency (η) and the characteristic temperature ( T o ) were 0.25 mW/mA and 53 K, respectively. Single longitudinal mode operation was attained up to 25 mW light output. These results show a great potential of MOCVD for the fabrication of InGaAsP/InP optical devices.

Growth of GaAs/AlGaAs quantum well structures using a large-scale MOCVD reactor

Abstract GaAs/AlGaAs quantum well structures were grown on 2 inch GaAs(100) substrates by a large-scale metalorganic chemical vapor deposition (MOCVD) reactor. The cross-sectional TEM images clearly showed quantum well structures which contained 20, 40, 70, 100, and 200 A thick GaAs wells. High resolution lattice images showed that the grading region at the heterointerface was no more than one half of a lattice constant. The photoluminescence (PL) peak energies for various well widths at room temperature agreed well with the calculated values based on the rectangular potential model. On the other hand, at 4.2 K the peak energy was lower than the theoretical value by 20 meV. The distribution of well widths was less than one half of a lattice constant for the whole wafers.

Study of initial buffer layer in GaAs-on-Si growth

Abstract An AlAs/GaAs low temperature buffer-layer (LTB) has been found to be effective for reducing the density of pit-defects in the GaAs layer grown on Si, which are the origin of micro-cracks. SEM observation has indicated that the Si surface is covered more smoothly and more uniformly by the AlAs/GaAs LTB rather than by conventional GaAs LTB. Consequently, the pit-defect density was remarkably reduced by employing the AlAs/GaAs LTB and the micro-crack free GaAs-on-Si with a GaAs thickness of 5 μm has been obtained.

High quality p-Cd0.22Hg0.78Te grown by liquid-phase epitaxy

Abstract We have systematically studied the growth conditions of Cd 0.22 Hg 0.78 Te liquid-phase epitaxy using an open-tube horizontal slider apparatus. Optimizing each parameter, we have reproducibly obtained high-quality p-Cd 0.22 Hg 0.78 Te epitaxial layers having an area of 15 × 20 mm 2 with the following characteristics: surface roughness of ± 0.5 μm, compositional uniformity of epitaxial layer of 0.220 ± 0.001, carrier concentration of 1 × 10 16 cm -3 at 77 K, and Hall mobility of 650 cm 2 /V·s at 77 K. These characteristics are suitable for production of high-performance integrated detector arrays.