Nobuyasu Hase

Monolithic integration of an InGaAsP/InP laser diode with heterojunction bipolar transistors

A monolithic integration of an InGaAsP laser diode together with current supplying circuit on a single InP substrate has been achieved. Heterojunction bipolar transistors (HBT’s) have been constructed utilizing the burying epitaxial layers of the buried heterostructure laser diode. The laser has been successfully modulated up to 1.6 GHz through the HBT’s driving circuit with sinusoidal electrical signal.

Deep Levels in InP Grown by MOCVD

Deep levels in the undoped InP grown by MOCVD have been investigated by deep level transient spectroscopy (DLTS). Three electron traps MOE1, MOE2, MOE3 have been observed with activation energies of 0.37 eV, 0.53 eV and 0.60 eV, respectively, in the temperature range between 160 K and 380 K. The trap concentrations of these levels were from 1013 cm-13 to 1015 cm-3 for samples with carrier concentrations of (1-6)×10-16 cm-3. The electron capture cross sections (σn) have been directly determined to be 3.1×10-18 cm2 (at 206 K) for MOE1 and 8.8×10-19 cm2 (at 344 K) for MOE3. For the level MOE2, it has been found that the capture cross section is strongly dependent on temperature, i.e., temperature dependence of this cross section is experimentally well-characterized by the relation σn=4.2×10-12 (cm2) exp (-0.38 (eV)/kT), which indicates the multiphonon emission process occurring during an electron capture event. Two deep levels have also been found in the LEC InP substrate material, which are identical to the defects observed in the epitaxial layer.

InP MESFET Grown by MOCVD

MESFET devices with 2 µm gate length have been fabricated on InP epitaxial layers grown by the MOCVD technique on Fe-doped semi-insulating InP substrates. The best electrical properties of InP epitaxial films have been measured and are n=2.7×1015 cm-3 and µ=3500 cm2/Vs at room temperature. The barrier height and the ideality factor of Au-n InP Schottky diode were estimated to be 0.66 eV and 1.18, respectively. Depletion mode n-channel MESFET has shown transconductance of ~90 mS/mm and the saturation drain current of ~20 mA at zero gate bias.

Raman scattering of InGaAsP lattice-matched to GaAs in the region of immiscibility

We have studied the Raman spectra of the InxGa1-xAsyP1-y quaternary alloys lattice-matched to GaAs in the immiscible region. The spectra exhibit four modes of behavior due to four binary compositions: GaP-, InP-, GaAs-, and InAs-like phonon modes. It was found that the phonon spectra in the immiscible region are well explained by the isodisplacement model of Inoshita [J. Appl. Phys. 56 (1984) 2056].

Fabrication and lasing characteristics of 1.3‐μm InGaAsP multiquantum‐well lasers

This paper reports the fabrication and lasing characteristics of 1.3‐μm InGaAsP multiquantum‐well (MQW) buried heterostructure (BH) lasers grown by liquid‐phase epitaxy (LPE) technique. The MQW active region consists of five InGaAsP well layers (λg=1.3‐μm, Lz∼200 A and InGaAsP barrier layers (λg=1.1 μm, d∼400–600 A). These lasers have threshold currents of 15–20 mA at 25 °C, external quantum efficiencies of 50% at 25 °C, and T0 values of 130–145 °K in the temperature range of less than 300 °K. The beam divergences perpendicular and parallel to the junction plane were in the narrow range of 10–13°. Furthermore, the polarization‐dependent gain‐current relationship between the TE and TM mode of InGaAsP MQW lasers has been investigated in detail for the first time.

A 1.3 µm InGaAsP/InP Multiquantum Well Laser Grown by LPE

We have successfully achieved a 1.3 µm InGaAsP/InP BH laser with multiquantum well active layers grown by low-temperature LPE technique (Tg=589°C). The thickness of thin epitaxial layers was less than de Broglie wavelength. The laser has a threshold current of 19 mA, an external differential quantum efficiency of ~40%, and T0 value of ~145 K in the range from -5°C to 20°C and ~60 K from 20°C to 70°C.

MOCVD Growth and Characterization of (AlxGa1-x)yIn1-yP/GaAs

We have demonstrated the MOCVD growth of AlGaInP under low pressure using a self-cracking system (SCS) for the group V hydride (PH3). In InGaP growth, the incorporation efficiency of In atoms for the SCS method is higher than that for the conventional method. For AlInP growth, however, efficiency did not depend on growth methods or growth temperatures. The compositions of AlGaInP are independent of PH3 flow rates and growth temperatures. These results indicate that it is easy to control the alloy compositions of the AlGaInP/GaAs system using the SCS method, even though growth conditions fluctuate slightly.

Raman Scattering Study of InGaAsP Quaternary Alloys Grown on InP in the Immiscible Region

We have studied the asymmetric broadening of the Raman spectra of InxGa1-xAsyP1-y grown on InP in the immiscible region using the spatial correlation model. The compositional dependence of Raman peaks are well explained by a simple model which does not account for the immiscibility. However, the broadening of the Raman line shape is greatly enhanced in the samples in the region of the immiscibility. In particular, the asymmetry of the spectral peak of the InAs-like longitudinal optical phonon is found to be enhanced in the immiscible region. This shows that the samples which include the immiscibility have been structurally changed to suppress the uniform distribution of the long wavelength phonons.

Raman Intensity of Phonon Modes in InGaAsP Quaternary Alloys Grown on (100) InP in the Region of Immiscibility

The Raman intensities of optical phonon modes in InxGa1-xAsyP1-y quaternary alloys lattice matched to (100) InP are studied in the compositional region of immiscibility. The peak intensity as well as the integral intensity of each phonon modes are investigated in terms of the relative density of corresponding bonds. It was found that the integral intensity is well interpreted in terms of the bond density. The replacement of a gallium atom with an indium atom produces a remarkable variation in the peak intensity.

A new cracking method for group V hydrides in the MOCVD growth using triethylindium (TEI)

Abstract We have demonstrated a new cracking method, which uses a self-cracking system (SCS), for group V hydrides such as PH 3 and AsH 3 in the MOCVD growth of In 1− x Ga x As y P 1− y and ( Al x Ga 1− x ) y In 1− y P using triethylindium (TEI) as a source material. The SCS can be explained as follows; PH 3 and/or AsH 3 are introduced by passing through a line located near the RF-heated susceptor into the reactor tube, resulting in pre-cracking of the PH 3 and/or AsH 3 before they are mixed with TEI. By the use of this SCS, we have found that the In atom is introduced into the solid more effectively than with conventional methods. In particular, for the case of the MOCVD growth of In 1− x Ga x As y P 1− y , it was found that the low-pressure-SCS (LP-SCS) method is most suitable for the incorporation of both In and P. Details of the growth conditions, electrical and optical properties of epitaxial layers are also presented. This SCS is one of the most promising techniques for the MOCVD growth of compound semiconductors using TEI.