Heng-Kuang Lin

An ultra-low power InAs/AlSb HEMT Ka-band low-noise amplifier

The first antimonide-based compound semiconductor (ABCS) MMIC, a Ka-Band low-noise amplifier using 0.25-/spl mu/m gate length InAs/AlSb metamorphic HEMTs, has been fabricated and characterized on a 75 /spl mu/m GaAs substrate. The compact 1.1 mm/sup 2/ three-stage Ka-band LNA demonstrated an average of 2.1 dB noise-figure between 34-36 GHz with an associated gain of 22 dB. The measured dc power dissipation of the ABCS LNA was an ultra-low 1.5 mW per stage, or 4.5 mW total. This is less than one-tenth the dc power dissipation of a typical equivalent InGaAs/AlGaAs/GaAs HEMT LNA. Operation with degraded gain and noise figure at 1.1 mW total dc power dissipation is also verified. These results demonstrate the outstanding potential of ABCS HEMT technology for mobile and space-based millimeter-wave applications.

An ultra-low power InAs/AlSb HEMT W-band low-noise amplifier

An antimonide-based compound semiconductor (ABCS) microstrip MMIC, a W-Band low-noise amplifier using 0.2-μm gate length InAs/AlSb metamorphic HEMTs, has been fabricated and characterized on a 50 μm GaAs substrate. The compact 1.2 mm 2 five-stage W-band LNA demonstrated a 3.9 dB noise-figure at 94 GHz with an associated gain of 20.5 dB. The measured dc power dissipation of the ABCS LNA was an ultra-low 1.2mW per stage, or 6.0 mW total which is less than one-tenth the dc power dissipation of a typical equivalent InGaAs/AlGaAs/GaAs HEMT LNA. Operation with degraded gain and noise figure at 3.5 mW total de power dissipation is also verified. These results demonstrate the outstanding potential of ABCS HEMT technology for mobile and space-based millimeter-wave applications.

In situ dimensional changes of powder injection-molded compacts during solvent debinding

Defects such as cracking, slumping, and sagging are frequently found in powder injection-molded (PIM) compacts. These defects are partly related to the swelling of the binders during solvent debinding. However, little quantitative analysis has been reported to date. The in situ length changes of PIM specimens during debinding were measured in this study using a laser dilatometer designed by the authors specifically for these experiments. A total linear expansion from 0.5 to 2% was observed and was influenced by the binder, the solvent type, and the debinding temperature. This expansion is attributed to the interaction between the solvent and the binder, particularly the insoluble backbone binder components such as low-density polyethylene and polypropylene. These in situ measurements on the length and temperature changes help explain how the defects formed during debinding. Based on the results observed, guidelines for designing binders and debinding schedules are recommended.

InAs/AlSb HFETs with f τ and f max above 150 GHz for low-power MMICs

Very low-power InAs/AlSb HFETs with excellent RF performance are reported. These metamorphic HFETs on GaAs substrates combine high microwave g/sub m/ of at least 1.1 S/mm with low parasitic resistances to offer simultaneous measured f/sub /spl tau// and f/sub max/ values of 160 GHz for both figures of merit. This performance is obtained at a drain bias voltage of only 0.35 V for an HFET with a 0.25-/spl mu/m gate length. The high current gain (f/sub /spl tau//) is attributable to the improved charge control due to scaling of the barrier thickness to 180 /spl Aring/. The maximum power gain (f/sub max/) depends on both g/sub m/ and the HFET output conductance, which is fundamentally limited by the low breakdown voltage gap of the InAs channel (E/sub g/ = 0.36 eV).

n/sup +/-InAs-InAlAs recess gate technology for InAs-channel millimeter-wave HFETs

We report a submicrometer, self-aligned recess gate technology for millimeter-wave InAs-channel heterostructure field effect transistors. The recess gate structure is obtained in an n/sup +/-InAs-InAlAs double cap layer structure with a citric-acid-based etchant. From molecular-beam epitaxy-grown material functional devices with 1000-, 500-, and 200-nm gate length were fabricated. From all three device geometries we obtain drive currents of at least 500 mA/mm, gate leakage currents below 2 mA/mm, and RF-transconductance of 1 S/mm. For the 200-nm gate length device f/sub /spl tau// and f/sub max/ are 162 and 137 GHz, respectively. For the 500-nm gate length device f/sub /spl tau// and f/sub max/ are 89 and 140 GHz, respectively. We observe scaling limitations at 200-nm gate length, in particular a negative threshold voltage shift from -550 to -810 mV, increased kink-effect, and a high gate-to-drain capacitance of 0.5 pF/mm. The present limitations to device scaling are discussed.

Device Characteristics of InGaSb/AlSb High-Hole-Mobility FETs

This letter reports the effect of growth temperature on carrier transport characteristics in In_0.4Ga_0.6Sb/AlSb heterostructure and demonstrates that hole mobility was enhanced by eliminating a parallel conducting channel in the buffer layers. Based on optimized growth conditions, hole mobility as high as 1220 cm²/V·s with carrier concentration of 1.3 ×10¹² cm^-2 was achieved. A 0.2- μm-gate-length In_0.4Ga_0.6Sb/AlSb p-channel device exhibited a maximum drain current of 102 mA/mm, a peak transconductance of 92 mS/mm, and an on-state breakdown voltage over 3 V. The pinchoff was observed for a gate bias of 0.6 V at drain current of 1 mA/mm. The current-gain and power-gain cutoff frequencies were 15 and 20 GHz, respectively.

Design and characteristics of strained InAs/InAlAs composite-channel heterostructure field-effect transistors

We report composite-channel heterostructure field-effect transistors (HFETs) with an InAs channel and an In0.9Al0.1As subchannel. The HFETs are grown on antimonide buffer layers. Two composite-channel structures with different planar Te doping schemes are designed, fabricated, and characterized. High radio-frequency transconductances of above 0.9 S/mm and ∼55GHz current gain cutoff frequencies are achieved in devices with 500 nm gates. Planar Te doping in the buffer layers reduces the high kink-effect currents otherwise found in InAs/AlSb HFETs, an effect which can be attributed to either increased breakdown field in the In0.9Al0.1As subchannel or to suppression of hole blocking in the buffer. The present limitations to device performance and suggested approaches for their elimination are discussed.

Thermal, Solvent, and Vacuum Debinding Mechanisms of PIM Compacts

Abstract The mechanisms of thermal, solvent, and vacuum debinding processes for powder injection molded (PIM) compacts were investigated. Mercury intrusion porosimetry (MIP) and scanning electron m...

RF noise performance of low power InAs/AlSb HFETs

In this paper, we report on the complete RF noise characteristics of a 0.25 /spl mu/m gate-length InAs/AlSb HFET exhibiting a minimum noise figure F/sub min/ less than 1 dB from 2-25 GHz. Energy band diagram and the DC characteristics of the HFET were analysed.

RF and DC characteristics of low-leakage InAs/AlSb HFETs

InAs/AlSb HFETs with excellent RF and DC properties are reported. The drain currents are 750 mA/mm. with peak transconductance g/sub m/ of 1.1 S/mm. The gate leakage is below 1 nA//spl mu/m/sup 2/ for low gate bias. The threshold voltages of 0.25 /spl mu/m and 0.5 /spl mu/m gate-length devices are -2.5 and -1.5 V respectively, indicating short channel effects are present. Small-signal measurements on a 0.25 /spl mu/m gate-length device show f/sub /spl tau// of 120 GHz and f/sub max/ of 100 GHz at drain voltages below 0.4 V.