A review is presented of the properties of interdigitated metal-semiconductor-metal (MSM) Schottky barrier photodetectors based on the InGaAs-InP material system, and the performance achieved by experimental devices is discussed. The experimental work concentrates on the barrier-enhanced lattice-matched InAlAs-InGaAs device grown by low pressure organometallic chemical vapor deposition (OMCVD), which has to date yielded detectors with the highest performance characteristics. Current research on their integration with FETs to form monolithic receivers and with waveguides for on-chip optical signal processing is also included. >

/pdf/ingaas-metal-semiconductor-metal-photodetectors-for-long-328jtxq3kp.pdf

InGaAs metal-semiconductor-metal photodetectors for long wavelength optical communications

Recent efforts are being focussed on improving the breakdown voltage (BV) of InAlAs/InGaAs MODFET's on InP towards high-power applications. A detailed understanding of the physics of breakdown in these devices is still lacking. In this paper, we carry out a study of off-state breakdown on state-of-the-art MODFET's in this material system. Through a combination of a surface-depleted cap and mesa-sidewall isolation the devices have BV's of around 10 V. We find that BV shows a negative temperature coefficient and also decreases with a higher InAs mole fraction in the channel. As we have recently found in InAlAs/n/sup +/-InGaAs HFET's, off-state breakdown appears to be a two-step process. First, electrons are emitted by thermionic-field emission from the gate to the insulator. Second, as a consequence of the large electric field in the insulator and the substantial /spl Delta/E/sub C/ between insulator and channel, they enter the channel hot, into the high-field drain-gate region, and relax their energy through impact-ionization. This combined hypothesis is able to explain why the MODFET breakdown voltage depends on both channel and insulator design parameters. >

Off-state breakdown in InAlAs/InGaAs MODFET's

The authors report electrical measurements on four different metal contacts which formed Schottky barriers to lightly doped complementary n- and p-type Al/sub 0.48/In/sub 0.52/As epitaxial material grown by molecular beam epitaxy on semi-insulating InP substrates. The Schottky contact metals studied were Au, Al, Pt, and tri-layer Ti/Pt/Au. The Schottky barrier heights varied from 0.560 eV for Al on n-type AlInAs to 0.905 eV for Al on p-type AlInAs, with intermediate values for the other metals studied. The sum of n- and p-type Schottky barrier heights for each metal contact ranged from 1.440 to 1.465 eV, in good agreement with the accepted Al/sub 0.48/In/sub 0.52/As bandgap value of 1.45 eV. >

Schottky barrier heights of n-type and p-type Al/sub 0.48/In/sub 0.52/As

The fabrication and microwave performance of heterostructure InAlAs/InGaAs HEMTs (high-electron-mobility transistors) and MESFETs are described. Maximum stable gains of 14.3 dB for a HEMT and 12 dB for a MESFET at 26.5 GHz have been achieved. These are believed to be record gains for FETs having gates as long as 0.7 mu m. >

High-performance InAlAs/InGaAs HEMTs and MESFETs

InAlAs/n/sup +/-InGaAs HFET's on InP have demonstrated a high breakdown voltage in spite of the narrow bandgap of the InGaAs channel. In order to understand this unique feature, we have carried out a systematic temperature-dependent study of off-state breakdown. We find that off-state breakdown at room-temperature is drain-gate limited and that the breakdown voltage shows a negative temperature coefficient. Based on these and other findings, we propose that off-state breakdown is a two-step process. First, electrons are injected by thermionic-field emission from the gate to the insulator. Second, electrons enter into the high-field drain-gate region of the channel hot, and relax their energy through impact-ionization. This combined mechanism explains our experimental observations that off-state breakdown in InAlAs/n/sup +/-InGaAs HFET's depends both on channel and insulator design. Our findings are relevant to other InAlAs/InGaAs HFET's, such as the MODFET, as well as HFET's based on other narrow-bandgap materials. >

Physics of breakdown in InAlAs/n/sup +/-InGaAs heterostructure field-effect transistors

The surface barrier heights φbn and room‐temperature band gaps Eg of Si‐doped InxAl1−xAs layers grown by molecular beam epitaxy on n‐type (100) oriented InP substrates have been determined as a function of composition with capacitance versus voltage, internal photoemission, photoluminescence, and double‐crystal x‐ray rocking curve measurements for 0.45 0.78, n‐type surfaces might be accumulated and p‐type surfaces are likely to be inverted.

C. L. Lin

Papers

Composition dependence of Au/InxAl1−xAs Schottky barrier heights