Kenya Nakai

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.

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.

Material and device properties of GaAs on sapphire grown by metalorganic chemical vapor deposition

Surface morphology, electron mobility, and photoluminescence (PL) spectrum have been investigated for the epitaxial layers of GaAs on (0001) sapphire grown at several temperatures. The optimum growth temperature range is determined to be around 690 °C. The mobility and the PL intensity efficiency are improved by increasing the layer thickness, due to the decrease of defect density. The structure related to the defects is located at a wavelength of 1.04 μm in the PL spectra. We fabricate the first field‐effect transistor on GaAs on sapphire, and it has a transconductance of 20 mS/mm for a gate length of 2.5 μm.

Residual Donors in High Purity Gallium Arsenide Epitaxially Grown from Vapor Phase

Residual impurities involved in a GaAs layer epitaxially grown from vapor phase are identified by far-infrared photoconductivity measurement. Silicon, selenium, sulfur and germanium are readily incorporated as shallow donors into GaAs epitaxial layers. The dominant residual donor is sulfur for epitaxial layers grown by Ga-AsCl3-N2 system and it is silicon or sulfur for epitaxial layers by usual Ga-AsCl3-H2 system. From spectral peaks of the photoconductivity in a magnetic field, the donor ionization energies for silicon, selenium, sulfur and germanium are estimated to be 5.759 meV, 5.812 meV, 5.845 meV and 5.949 meV respectively.

Photoluminescence Study of Carbon Doped Gallium Arsenide

The photoluminescence studies of the carbon doped epitaxial gallium arsenide revealed that a pair of emission bands at 1.493 eV (B-A) and 1.490 eV (D-A) were attributed to the carbon acceptor on arsenic site. The sharp doublet emission lines at 1.5127 eV and 1.4937 eV were identified with the exciton recombination bound to a neutral carbon acceptor and the two-hole transition in which the neutral carbon acceptor is left in an excited state, respectively. From the observation of these emissions, the 1S3/2 ground and 2S3/2 excited state energies of carbon acceptor were found to be 26.5 meV and 7.5 meV above the valence band edge, respectively. The results were supported by the effective mass arguments and by the dependence of the binding energy on the atomic number of impurities.

High‐speed monolithically integrated GaAs photoreceiver using a metal‐semiconductor‐metal photodiode

A planar monolithically integrated GaAs photoreceiver involving a transimpedance preamplifier has been fabricated using a metal‐semiconductor‐metal (MSM) photodiode. The present MSM photodiode showed a small capacitance of 0.14 pF, which is much smaller than in conventional p‐i‐n photodiodes, and a high‐speed pulse response exhibiting a rise time of 300 ps was demonstrated. It is shown that an MSM photodiode is suitable for monolithic integration due not only to the simple process but also because of its high‐speed operation.

Monolithic integration of a pin photodiode and a field‐effect transistor using a new fabrication technique—graded step process

A new fabrication technique of optoelectronic integrated circuit’s (OEIC’s), the graded step process, has been developed and found to improve the photolithographic yield and the overall process reproducibility. By applying this technique, a laterally integrated pin photodiode/field‐effect transistor has been fabricated and shown to exhibit a high‐speed response and a high sensitivity. This result indicates the potential of this process for applications to larger scale OEIC’s.

AlGaAs/GaAs p‐i‐n photodiode/preamplifier monolithic photoreceiver integrated on a semi‐insulating GaAs substrate

A fully monolithic photoreceiver circuit incorporating an AlGaAs/GaAs p‐i‐n photodiode and a GaAs field‐effect transistor based transimpedance amplifier has been fabricated in the form of a horizontally integrated structure on a semi‐insulating GaAs substrate. Parasitic capacitances of the circuit elements have been minimized in the present monolithic circuit, and a short rise and fall time of 1.0 ns, corresponding to an approximate −3 dB frequency of 300 MHz, has been demonstrated at the internal feedback resistance of 1.3 kΩ. Preliminary measurement of the noise characteristics of the present circuit has exhibited an encouraging value of the equivalent input noise current of 13 pA Hz−1/2 at 300 MHz.

Activation ratio of Fe in Fe‐doped semi‐insulating InP epitaxial layers grown by liquid phase epitaxy and metalorganic chemical vapor deposition

The activation ratio of Fe atoms introduced in semi‐insulating (SI) InP layers grown by liquid phase epitaxy (LPE) and metalorganic chemical vapor deposition (MOCVD) has been investigated, employing the current‐voltage characteristics of n+‐SI‐n+ InP diodes and secondary ion mass spectroscopy analysis. The result indicates that most Fe atoms in LPE‐grown SI layers are electrically active as deep acceptors; however, a large amount of unactivated Fe atoms are present in MOCVD‐grown SI layers. This difference between the two kinds of Fe‐doped SI layers can be attributed to the difference in the growth mechanisms of LPE and MOCVD.

A WSi/TiN/Au Gate Self-Aligned GaAs MESFET with Selectively Grown n+-Layer using MOCVD

A WSi/TiN/Au gate self-aligned GaAs MESFET was formed using MOCVD. The WSi/TiN/Au gate acts as a selective growth mask for the n+-layer. This new process is demonstrated to be effective for reducing the gate resistance and source resistance of FETs simultaneously. The gate resistance, Rg, was 3.4 Ω (Lg=1.3 um, Wg=30 um) and was reduced one tenth compared to that of the WSi gate. A high-speed MSI and high performance microwave device can be obtained by using the WSi/TiN/Au gate self-aligned GaAs MESFETs.