Fe-doped Semi-insulating InP Substrate Research Articles

Nonalloyed high temperature ohmic contacts on Te-doped InP

We report on a thermal stability study of WSi0.79 contacts on Te-doped InP. The epitaxial InP layers were grown on Fe-doped semi-insulating InP substrates by metalorganic molecular beam epitaxy. Tri-isopropylindium-di-isopropyltellurium was used as the Te precursor and the doping level was 1.4×1020 cm−3. Contact metal, amorphous WSi0.79, was sputtered from a composite and an excellent specific contact resistance of 1×10−6 Ω cm2 was achieved. The specific contact resistivity was also measured at different temperature (25–200 °C) and it stayed fair contact. This is clear indication that the current transport through the contact dominates by tunneling. After alloying at temperatures up to 600 °C, there is no obvious change of specific contact resistance or sheet resistance. After 700 °C annealing, there was significant P out-diffusion detected and the specific contact resistance began to degrade. However, the contact metal morphology and edge definition were unaffected. After 800 °C annealing, there was evidence of In out-diffusion after and the surface morphology became rough.

Piezoreflectance study of InP near the absorption edge

Piezoreflectance measurements were carried out on InP samples with different doping concentrations near the absorption edge in the temperature range between 20 and 300 K. We show that the large features often found below the bandgap in piezomodulated spectra of InP samples are related not only to the impurity states but also to the back-surface reflection effects. Their proximity to the band edge depends on temperature, the impurity species and the geometry of the species in which the multiple reflections occur. At the band edge, the Burstein - Moss shift for the heavily S-doped InP and a pronounced excitonic effect for the Fe-doped semi-insulating InP substrates are observed. In addition, the temperature dependence of the energy position and broadening parameter of the excitonic and direct-bandgap transition features are also evaluated. The expression eV is proposed for the temperature dependence of the semi-insulating InP bandgap over the temperature range 20 - 300 K.

Laser-assisted thermally enhanced InP via etching for microwave device applications

A laser-based technique for thermally enhanced rapid etching of via holes through Fe-doped semi-insulating InP substrates is described. The process produces steep-walled closely-spaced via holes in etch times as short as 3-5 s/via in 100- mu m-thick substrates. This technique is key to the fabrication of low-inductance metallized via contacts critical for high-speed microwave and millimeter-wave devices and circuits. The laser-based technique is material selective, allowing both through-wafer and blind-hole etching which is terminated on metal circuit contacts. Via structures have been fabricated on semi-insulating InP substrates patterned with millimeter-wave device geometries. >

Fabrication/Characterization of a Pseudomorphic Ga0.1In0.9P/InP MESFET

ABSTRACTA pseudomorphic Ga0.1In0.9P/InP MESFET grown by low pressure metalorganic chemical vapor deposition(LP-MOCVD) has been fabricated and characterized. The results indicated a transconductance of 66.7 ms/mm and a saturation drain current (Idss) of 55.6 mA have been achieved; furthermore, the Schottky barrier on InGaP as high as 0.67eV can be obtained using Pt2Si as the gate material. For comparison, a conventional InP MESFET with 5μm gate length has also been fabricated on InP epitaxial layer grown by low pressure metalorganic chemical vapor deposition on Fe-doped semi-insulating InP substrate. The transconductance and Idss were found to be 46.7 mS/mm and 43.1 mA at zero gate, respectively, for the depletion mode n-channel MESFET with Au as the gate metal; whereas, for the MESFET using Pt2Si as the gate metal, a transconductance of 40.3 mS/mm and a saturation drain current of 41.1 mA at zero gate bias have been obtained. The results indicated that Ga0.1In0.9P/lnP MESFET has better performance than InP MESFET because of higher energy gap of Ga0.1In0.9P.

The phototransistor revisited: all-bipolar monolithic photoreceiver at 2 Gb/s with high sensitivity

The authors revisit the three-terminal phototransistor and demonstrate the application of the HPT (heterojunction phototransistor) at 2 Gb/s in an all-bipolar monolithic photoreceiver. They also show a performance comparable to the best p-i-n photoreceiver. The phototransistors were fabricated from epitaxial layers grown by metal-organic molecular beam epitaxy on a Fe-doped semi-insulating InP substrate. The phototransistor had a small-signal electrical current gain between 150 and 200. The quantum efficiency of the base-collector photodiode was 40%. Microwave on-wafer measurements yielded a unity current gain cutoff frequency of 30 GHz and a maximum oscillation frequency of 20 GHz at a collector current of 5.0 mA. The small-signal frequency response of the packaged monolithic photoreceiver indicated a 3-dB bandwidth of 1.1 GHz, at a wavelength of 1.53 mu m, with no peaking in the response.

Manganese-related luminescence in GaInAs/AlInAs multiple quantum wells grown on InP by molecular beam epitaxy

Two Mn-related luminescence peaks have been observed in a series of nominally undoped Ga0.47In0.53As/Al0.48In0.52As multiple quantum wells (MQW) grown lattice-matched on InP substrates by molecular beam epitaxy. These two peaks correspond to on-center and on-edge impurity states, respectively. The origin of the Mn impurities is outdiffusion from the Fe-doped semiinsulating InP substrate into the epitaxial layer. The binding energy of Mn acceptors, determined to be 53±3 meV in bulk-like Ga0.47In0.53As, increases to 80±5 meV for the on-center Mn state in a 58 A MQW. The strong well-width dependence of the binding energy is explained in terms of the unique behavior of the Mn impurity in III–V semiconductors. The Mn in Ga0.47In0.53As and Ga0.47In0.53As/Al0.48In0.52As MQWs behaves predominantly as a deep impurity.

High-speed and high-power GaInAsp/InP junction field-effect transistor with submicron gate

Depletion-mode GaInAsP/InP junction field-effect transistors have been fabricated on Fe-doped semi-insulating InP substrates using liquid-phase epitaxial growth techniques. We achieved transconductance of 24 mS (l60mS/mm), drainsource saturation current at an on gate bias of 486mA/mm and current cutoff frequency of 18.8 GHz using a GaInAsP channel layer owing to the gate length reduction.

Electrical and optical properties of InP grown by MBE using P + ion beam

InP layers have been grown on Fe-doped semi-insulating InP substrates by molecular beam epitaxy using a low energy P + ion beam under various conditions: V/III flux ratios were from 1.2 to 2.2, and growth temperatures were from 400 to 490°C. The electrical and optical properties of the epilayers are described. The unintentionally doped epilayers were n-type, and there existed two shallow donor levels with activation energies of 4 and 7 meV and two deep donor levels with activation energies of 125 and 175 meV. The carrier concentration and mobility increased with decreasing V/III flux ratio and/or increasing growth temperature. The carrier concentration and mobility measured at 80 K were 1.2x10 16cm -3 and 21200 cm 2/V°s for the sample grown at 490°C and with a V/III flux ratio of 1.9. Photoluminescence spectra and SIMS profiles showed that Fe atoms diffuse into epilayers from substrates and pile up near the surface.

Microwave performance of ion-implanted InP JFETs

These devices have a planar structure with the channel and gate regions formed by the selective implantation of silicon and beryllium into an Fe-doped semi-insulating InP substrate. The nominal gate length is 2 mu m with a channel doping of 10/sup 17/ cm/sup -3/ and thickness of 0.2 mu m. The measured values of f/sub T/ and f/sub max/ are 10 and 23 GHz, respectively. Examination of the equivalent circuit parameters and their variation with bias led to the following conclusions: (a) a relatively gradual channel profile results in lower than desired transconductance, but also lower gate-to-channel capacitance; (b) although for the present devices, the gate length and transconductance are the primary performance-limiting parameters, the gate contact resistance also reduces the power gain significantly; (c) the output resistance appears lower than that of an equivalent GaAs MESFET, and requires a larger V/sub DS/ to reach its maximum value; and (d) a dipole layer forms and decouples the gate from the drain with a strength that falls between that of previously reported GaAs MESFETs and InP MESFETs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Monolithically integrated enhancement-mode InP MISFET inverter

Three InP MISFETs have been monolithically integrated on an Fe-doped semi-insulating InP substrate in conjunction with three integrated load resistors forming an inverter. The epitaxial layers have been grown by chloride vapour-phase epitaxy. The MISFETs exhibit transconductances as high as 200 mS/mm for a gate length of 1 μm. The circuit consists of one MISFET that is operated as a one transistor-inverter stage in isolation and a two-stage inverter whose output is connected to the gate of an FET. For two-stage inverters we have obtained typical high- and low-level noise margins of 0.4 and 0.3 V at a bias level of 1.5 V.

Monolithically integrated In 0.53 Ga 0.47 As-PIN/InP-MISFET photoreceiver

In0.53Ga0.47As PIN photodiode and InP MISFET were monolithically integrated on an Fe-doped semi-insulating InP substrate. Photoreceiver sensitivities were measured at 100 Mbit/s NRZ pseudorandom signals.

Microwave gain from an n -channel enhancement-mode InP m.i.s.f.e.t.

A power gain of 14 dB at 1 GHz has been demonstrated in an enhancement-mode m.i.s.f.e.t. constructed on an Fe-doped semi-insulating InP substrate. The same device also exhibits well behaved gain characteristics at low frequencies.