T. Sanada

Planar selective growth of InP by MOVPE

The selective epitaxial growth of InP was studied using atmospheric MOVPE. The selective embedded growth of the mesa stripe and the calculation of the diffusion equation around the mesa stripe were performed. In addition to the facet growth of the {111}B planes, the diffusion process of the source species in the vapor phase is a dominant factor in controlling the shape in the vicinity of the mesa. To achieve planar selective growth of the mesa stripe, the use of a SiO2 mask with eaves on the top of the mesa is effective. This suppresses the anomalous growth at the top of the mesa as predicted from the calculations. A mesa height of less than 3 μm was found to be essential to planar growth. A high-performance planar InGaAsP/InP buried heterostructure laser was successfully fabricated using this process.

Direct observation of electron leakage in InGaAsP/InP double heterostructure

The electron leakage through the heterobarrier consisting of a thin InGaAsP active layer and a p‐InP confining layer was directly observed by using a novel InGaAsP/InP light‐emitting diode (LED) structure. In the present structure, electrons leaking from the active layer were confined in a subsidiary quaternary layer having a crystal composition different from that of the active layer, and the recombination emission caused by these electrons was optically detected. Experimental results showed that significant electron leakage can occur in the present InGaAsP/InP double heterostructure (DH) system, suggesting a possibility of the electron leakage being one of the dominant mechanisms of sublinearity in the light intensity‐current characteristics in InGaAsP/InP DH LED’s operating at wavelengths shorter than 1.3 μm and also of the temperature dependence of threshold current in laser diodes.

Ohmic Contacts to p-GaAs with Au/Zn/Au Structure

A reproducible technique for forming ohmic contacts with low contact resistances to p-GaAs is presented. A Au/Zn/Au multilayer structure, which is deposited by sequential evaporation of Au, Zn and Au, is found to realize a satisfactorily low specific contact resistance rc. The value of rc is minimized when the initial thickness of Zn layer is larger than 200 A and the alloying temperature is around 400°C. The minimum value of rc in Ω-cm2 is expressed as rc=1.8×1018p-1.3, where p is the net hole concentration in cm-3. It is also confirmed by Auger spectroscopy that the reduction of rc is caused by the preferential incorporation of Zn atoms into the GaAs bulk during alloying.

Planar‐embedded InGaAsP/InP heterostructure laser with a semi‐insulating InP current‐blocking layer grown by metalorganic chemical vapor deposition

We used metalorganic chemical vapor deposition to fabricate a planar‐embedded InGaAsP/InP heterostructure laser with a semi‐insulating InP current‐blocking layer. The laser exhibits cw operation with a low, 20 mA threshold current and a high external differential quantum efficiency of 40% at room temperature. Measurements have also shown a small‐signal frequency response of 10 GHz due to an extremely small parasitic capacitance of 3.5 pF.

Monolithic integration of a low threshold current quantum well laser and a driver circuit on a GaAs substrate

An AlGaAs/GaAs graded‐index waveguide separate‐confinement heterostructure (GRIN SCH) laser and a laser driver circuit composed of four GaAs metal‐semiconductor field‐effect transistors have been monolithically integrated on a semi‐insulating GaAs substrate. By introducing the GRIN SCH single quantum well (6 nm thick) structure, the integrated laser has exhibited room‐temperature cw operation characteristics with an extremely low threshold current of 15 mA as well as a high quantum efficiency of 50%. Measurements have also shown the conversion ratio of laser output power to input gate voltage of 4.3 mW/V, and the turn‐on and turn‐off times of the light output of 400 and 900 ps, respectively, demonstrating high sensitivity and fast response performance of the present monolithic laser/driver.

Monolithic integration of an AlGaAs/GaAs multiquantum well laser and GaAs metal‐semiconductor field‐effect transistors on a semi‐insulating GaAs substrate by molecular beam epitaxy

AlGaAs/GaAs multiquantum well lasers and GaAs metal‐semiconductor field‐effect transistors have been monolithically integrated on a semi‐insulating GaAs substrate by using molecular beam epitaxy. This integrated laser has exhibited cw operation with the low threshold current of 20 mA at room temperature. The laser/field‐effect transistor (FET) characteristics, such as a linear control of laser output power by changing the FET gate voltage, have been confirmed. A conversion ratio of laser output power to FET gate voltage has been measured to be as high as 3.3 mW/V. Rise and fall times of 1 ns have been demonstrated.

Optoelectronic integrated four-channel transmitter array incorporating AlGaAs/GaAs quantum-well lasers

A four-channel optoelectronic integrated transmitter array which is fabricated on a single GaAs substrate and operates at 834 nm is described. Each of the circuits incorporates a laser, a photodiode for laser power monitoring, and a laser driver circuit consisting of three GaAs field-effect transistors and a resistor. Laser threshold current of 15-21 mA, transmitter conversion efficiency of approximately 6 mW/V and high-speed operation at a bit rate of more than 1.5-Gb/s NRZ with allowable crosstalk have been demonstrated. A preliminary aging test of the lasers indicated that their stability is comparable to that of discrete devices. The results have demonstrated the feasibility of applying the transmitter array to optical components that process multichannel optical signals at high speed. >

Four‐channel AlGaAs/GaAs optoelectronic integrated transmitter array

A monolithic four‐channel optical transmitter at 0.8 μm wavelength has been fabricated. This has been achieved by using AlGaAs/GaAs optoelectronic integrated circuit (OEIC) approach. The OEIC chip contains four transmitter channels and each channel is composed of a graded‐index waveguide separate‐confinement heterostructure single quantum well laser, a monitor photodiode, and a laser driver circuit. The characteristics have been shown to be very uniform over four channels and pulse modulation responses over 1 Gb/s have been achieved.

Mechanism of catastrophic degradation in InGaAsP/InP double‐heterostructure light emitting diodes and GaAlAs double‐heterostructure light emitting diodes applied with pulsed large current

Catastrophically degraded InGaAsP/InP double‐heterostructure light emitting diodes and GaAlAs double‐heterostructure light emitting diodes, by application of pulsed large current, were investigated by photoluminescence topography, electroluminescence topography, etching technique, transmission electron microscopy, and energy dispersive x‐ray spectroscopy. In the case of InGaAsP/InP double‐heterostructure light emitting diodes, several dark‐spot defects and dark regions extending from the dark spot defects, were observed in the electroluminescence image of the light emitting region. By transmission electron microscopic observation, the dark defects were proved to be associated with mixed regions consisting of (i) micrograins of the matrix crystal, (ii) an amorphous area of the matrix crystal, and (iii) regions where the matrix crystal was alloyed with the metals of the electrode. An analysis by energy dispersive x‐ray spectroscopy indicated that the dark regions consist of large amounts of Au. These defect...

An Improved Technique for Fabricating High Quantum Efficiency Ridge Waveguide AlGaAs/GaAs Quantum Well Lasers

A technique has been developed for improving the quantum efficiency and the temperature stability of ridge waveguide AlGaAs/GaAs quantum well lasers. Excellent lasing characteristics, including a differential quantum efficiency of 75%, have been achieved in graded-index waveguide separate-confinement heterostructure single quantum well lasers fabricated by this technique.