Kyushik Hong

InGaAs/InP thermoelectric infrared sensor utilizing surface bulk micromachining technology

A novel InGaAs/InP micromachined thermoelectric sensor is presented. The key features of the reported sensors are the high thermal resistivity and high mobility of InGaAs lattice matched to InP, combined with a value of Seebeck coefficient that is acceptable for such applications. The anisotropic and selective surface bulk micromachining properties of this material system were successfully applied to devices aligned along the [010] orientation on a [100] InP wafer and the details of the technology used for this purpose are presented. A responsivity of 184 V/W and a relative detectivity of 7.1/spl times/108 cm Hz/sup -1/2//W have been demonstrated using this new sensor approach.

Growth and characterization of heavily carbon doped InGaAs lattice matched to InP by LP-MOCVD using liquid CCl 4

The growth of heavily carbon dopedp-InGaAs (~6.5xl019cm-3) lattice-matched to InP is reported. Growth is achieved by low pressure metalorganic chemical vapor deposition (LP-MOCVD) using all methyl metalorganic sources and liquid CC14. The impact of growth temperature and CC14 flow rates on growth rate reduction and alloy compositional change was investigated. Post-growth isothermal and isochronal annealing experiments were performed on the carbon doped InGaAs layers and a quantitative analysis of carrier activation is presented using Hall and secondary ion mass spectroscopy measurements. Reduced self-compensation by carbon displacement from indium to arsenic site, as well as, reduced hydrogen passivation are suggested as possible mechanisms responsible for carrier activation upon thermal annealing.

InGaAs-Schottky contacts made by in situ plated and evaporated Pt-an analysis based on DC and noise characteristics

The choice of plated versus evaporated Pt Schottky anode formation technology is shown to have a significant impact on junction quality and the noise temperature of InGaAs mixer diodes. The investigated diode layers were grown in-house via Metalorganic Vapor Phase Epitaxy (MOVPE) on an S.I. InP wafer. For anode diameters at and below 2 /spl mu/m, plated anodes clearly show superior fabrication (/spl sim/80%) yields relative to evaporated (below /spl sim/5%). DC and low-/high-frequency noise characteristics were compared, as functions of DC current drive, for plated versus evaporated InGaAs Schottky contacts at 10 Hz-100 kHz and 1.4 GHz for 4- and 6- /spl mu/m anode diameters. Plated anodes show distinctly lower ideality factors of /spl sim/1.2 versus /spl sim/1.4-1.66 for evaporated anodes. Plated Schottky contacts showed 5.5 dB lower noise levels in the range of 10 Hz-100 kHz and a lower noise temperature (220 K versus 360 K) at 1.4 GHz. Overall, relative to conventional evaporated Pt, plated Pt anode technology offers superior fabrication yield and should lead to higher receiver sensitivity especially when low IF frequencies are used.

MOVPE-grown millimeter-wave InGaAs mixer diode technology and characteristics

The merits of InGaAs-based millimeter-wave mixer diodes are explored experimentally and theoretically. Schottky junctions on InGaAs exhibit barriers (/spl phi//sub b/) in the neighborhood of 0.25 eV. The high mobility of InGaAs contributes to the low n/sup +/ sheet resistances of 1.9-5 /spl Omega//square for 1-/spl mu/m n/sup +/ InGaAs layers (n/sub s/=1.5/spl times/10/sup 19/ cm/sup -3/, /spl mu//sub n/=1800 cm/sup 2//V/spl middot/s) grown with our in-house Metalorganic Vapor Phase Epitaxy (MOVPE) system, The design, material growth, fabrication, and characterization of InGaAs integrated mixer/antennae are reported. Pt plating technology, adapted here for InGaAs Schottky contacts, has improved the ideality factor (/spl eta/) and yield relative to conventional evaporated Pt. With 810 /spl mu/W of local oscillator power, applied to the diode, and zero DC bias, an integrated InGaAs mixer/antenna demonstrated an excellent diode performance of 199 K RF input double-sideband noise temperature with a corresponding single-sideband (SSB) conversion loss (L/sub c/) of 5.0 dB at LO, RF, and IF frequencies of 94 GHz, 94 GHz/spl plusmn/1.4 GHz, and 1.4 GHz, respectively. Likewise, the diodes in an InGaAs subharmonic integrated mixer/antenna demonstrated an equivalent RF-port double-sideband (DSB) noise temperature (T/sub mix/) of 1058 K and single-sideband conversion loss of 10.2 dB at 180 GHz with a 90-GHz LO power (PLO) of 1.6 mW. Compared to GaAs diodes with RF coupling and IF losses removed, the single-ended InGaAs noise temperature results were within 46-100 K of those for state-of-the-art GaAs mixer diodes while requiring significantly less LO power.

Power performance of InGaAs/InP single HBTs

Typically, the microwave power characteristics of InP/InGaAs SHBTs have not been addressed due to their relatively inferior DC characteristics when compared to DHBTs, which implies early breakdown and thus limited power performance. On the other hand, SHBTs are very attractive for higher frequency applications due to the absence of the heterojunction spike at the base-collector (B-C) interface. Moreover, the homojunction B-C structure offers direct compatibility for HBT integration with PIN diodes, since the latter can be realized by using the B-C-subcollector region. Such integration is needed not only for OEICs but also for MMICs with switching capabilities. This paper reports for the first time a systematic investigation of InP-based SHBT characteristics and demonstrates their suitability for power applications.

Deep Level Characterization of LP-MOCVD Grown Al 0.48 In 0.52 As

Deep levels in unintentionally doped A1 0. 48 In 0.52 As layers epitaxially grown on InP substrates by low-pressure MOCVD have been investigated as a function of growth temperature (T g ranging from 570 to 690°C). Two different origins for the residual carrier concentration are deduced depending on Tg: i) low growth temperatures favor the creation of a deep donor located at E c -(0.13±0.04)eV; ii) At higher T g , a preferential incorporation of a shallow donor occurs, which can be attributed to silicon by SIMS measurements. The oxygen contamination deduced by SIMS and the electrical characteristics of the AlInAs layers do not appear to be correlated.

MOCVD growth parameter study of InP-based materials for high-performance HEMTs

Metal organic chemical vapor deposition (MOCVD) has been a very attractive technique for the epitaxial growth of III-V compound semiconductors for microwave and optoelectronic device applications due to its simplicity and flexibility. As in many other growth techniques, MOCVD requires the optimization of the growth conditions to obtain desirable material properties for specific applications. InAlAs/InGaAs HEMTs have demonstrated excellent electrical characteristics using MBE grown structures and more recently MOCVD grown devices have also shown promising but not yet equivalent performance. It is therefore important to perform a systematic evaluation of the growth criteria determining the properties of InP-based HEMTs grown by MOCVD. It is the purpose of this paper to address the issue of MOCVD growth criteria and to provide experimental validation for them by demonstrating state of the art device characteristics.<<ETX>>

The effect of growth interruption on the properties of InGaAs/InAlAs quantum well structures

The effect of the growth interruption time during the growth of InGaAs/InAlAs quantum well structures is shown to have a significant effect on both the interband transitions, as determined by photoreflectance, and the electrical properties of the as-grown structure. The results show that, for increasing growth interruption time, the quantum well heterointerfaces become more abrupt and the carrier mobility increases, thereby demonstrating that long interruption times are preferable for the growth of high quality rectangular quantum well structures.

Properties of InGaAs/InP thermoelectric and surface bulk micromachined infrared sensors

We present a concept for the realization of InGaAs/InP micromachined thermoelectric sensors. The advantages of InGaAs lattice matched to InP combine perfectly for this application. The high selectivity of wet chemical etching of InP against InGaAs is ideally suited for surface bulk micromachining. Thermoelectric InGaAs sensors profit from the high thermal resistivity combined with high electrical conductivity and Seebeck effect. Thanks to the material parameters a responsivity of 257 V/W and relative detectivity of 6.4×108 cm Hz−1/2/W are expected for infrared sensors.

Phase-controlled metal-organic chemical vapor deposition epitaxial growth of GaN on GaAs(100) using NH3

Abstract Cubic and hexagonal GaN epitaxial films were grown on GaAs(100) substrates by low pressure metallorganic chemical vapor deposition using NH 3 as a nitrogen source. Analysis of X-ray diffraction spectra and transmission electron microscopy measurements show a transformation from (0002) hexagonal or (111) cubic phase to (200) cubic phase GaN as the growth temperature is raised from 530 to 600 °C. The hexagonal phase is found to dominate as the temperature is further increased above 650 °C while the cubic phase dominated in the range of 570–650 °C. Selected-area electron diffraction and electron micro-diffraction tests confirm the results. The full width at half-maximum of the (200) diffraction peak from cubic GaN grown at 600 °C was about 1°, independent of V/III ratio (3000–7500) and for thickness up to 1 μm.