Malin Borg

Electrical Characterization and Small-Signal Modeling of InAs/AlSb HEMTs for Low-Noise and High-Frequency Applications

Electrical characterization and modeling of 2 times 50 mum gatewidth InAs/AlSb HEMTs with 225 nm gate-length have been performed. The fabricated devices exhibited a transconductance gm of 650 mS/mm, an extrinsic cutoff frequency fT and an extrinsic maximum frequency of oscillation fmax of 120 and 90 GHz, respectively, already at a low VDS of 0.2 V. A minimum noise figure less than 1 dB between 2-18 GHz was achieved at a dc power consumption of only 10 mW/mm. This demonstrates the potential of InAs/AlSb HEMTs for low-power, low-noise applications. To account for the elevated gate-leakage current lG in the narrow-bandgap InAs/AlSb HEMT, the conventional field-effect transistor small-signal model has been extended. The relatively high IG was modeled by shunting both Cgs and Cgd with Rgs and .Rgd, respectively. As a result, the small-signal S-parameters were more accurately modeled, especially for frequencies below 10 GHz. Utilizing this modeling approach, excellent agreement was obtained between measured and modeled S-parameters, unilateral power gain U (Masons gain) and stability factor K.

Gate-Recess Technology for InAs/AlSb HEMTs

The gate-recess technology for Si delta-doped InAs/AlSb high-electron-mobility transistors (HEMTs) has been investigated by combining atomic force microscopy (AFM) inspection of the gate-recess versus time with electrical device characterization. Deposition of the gate metal on the In0.5Al0.5As protection layer or on the underlying AlSb Schottky layer resulted in devices suffering from high gate-leakage current. Superior dc and high frequency device performance were obtained for HEMTs with an insulating layer between the gate and the Schottky layer resulting in a reduction of the gate leakage current IG by more than two orders of magnitude at a drain-to-source voltage VDS of 0.1 V. The existence of this intermediate insulating layer was evident from the electrical measurements. AFM measurements suggested that the insulating layer was due to a native oxidation of the AlSb Schottky layer. The insulated-gate HEMT with a gate length of 225 nm exhibited a maximum drain current ID higher than 500 mA/mm with good pinchoff characteristics, a dc transconductance gm of 1300 mS/mm, and extrinsic values for cutoff frequency fT and maximum frequency of oscillation fmax of 160 and 120 GHz, respectively.

(Cl2:Ar) ICP/RIE Dry Etching of Al(Ga) Sb FOR AlSb/InAs HEMTs

Dry etching of AlSb and Al_0.80Ga_0.20Sb has been performed by inductively coupled plasma/reactive ion etching based on a (Cl₂:Ar) gas mixture without addition of BCI₃. The dry etch process has been used to fabricate AlSb/InAs high electron mobility transistors isolated by a shallow mesa. Good DC/RF results, with extrinsic f_T/f_max= 135/105 GHz, have been measured for a 2times50 mum HEMT with a gate length of 295 nm.

Effect of Schottky layer thickness on DC, RE and noise of 70-nm gate length InP HEMTs

The Schottky layer thickness of 70-nm InP HEMTs has been studied with respect to DC, RF and noise performance. An optimum gate-to-channel distance between 13-14 nm was found. Biased at a drain-to-source voltage of 0.7 V, a 2times50 mum device exhibited an extrinsic transconductance, gm, of 1.1 mS/mm. The maximum frequency of oscillation, fmax, and the transit frequency, fT, were extracted to 200 GHz and 170 GHz, respectively. A 50 Omega noise temperature of 140 K was measured at room temperature

Monolayers and nanoparticles on nickel silicide for molecular electronics

We describe the use of nickel silicide as an electrode in molecular electronics applications. Formation of monolayers of aliphatic and aromatic hydrocarbons on nickel silicide is demonstrated, and these monolayers are used to link CdSe nanocrystals to the substrate. Using the conjugated linker molecule 1,4-ethynylphenyl-2′-nitro-1-benzene-dithiolate, scanning tunneling spectroscopy measurements at 120K show evidence of Coulomb blockade and resonant tunneling behavior associated with the nanocrystals. These measurements demonstrate the feasibility of using nickel silicide as an electrode in molecular electronic devices.

Vertical scaling of gate-to-channel distance for a 70 nm InP pseudomorphic HEMT technology

DC and HF performance for a 70 nm InP PHEMT technology have been studied as a function of gate-to-channel distance. The optimized PHEMT exhibited a maximum transconductance of 1.5 S/mm and f/sub max/ of 400 GHz.

Characterization of insulated-gate versus schottky-gate InAs/AlSb HEMTs

Fabrication and characterization of 225 nm gate-length InAs/AlSb HEMTs with excellent RF performance are reported. We show the importance of an insulating layer between the gate and the semiconductor to improve g_m, f_T and f_max, and most important from a noise perspective, the gate-leakage current I_G. By using an insulated-gate, I_G was reduced by two orders of magnitude. The insulated-gate HEMTs exhibited extrinsic f_T and f_max of 155 GHz and 115 GHz, respectively, at V_DS=0.5 V.

DC and RF Performance of 0.2-0.4 /spl mu/m Gate Length InAs/AlSb HEMTs

InAs/AlSb HEMTs with gate lengths in the range 225-335 nm processed on the same wafer have been investigated with respect to DC and RF performance. While the magnitude of the transconductance gm was similar for all gate lengths, the shortest gate length HEMT exhibited the highest extrinsic maximum frequency of oscillation fmax and extrinsic current gain cut-off frequency fT of 115 GHz and 165 GHz, respectively.

Benchmarking of low band gap III-V based-HEMTs and sub-100nm CMOS under low drain voltage regime

this works reports on speed and high performance benchmarking of low band gap III-V based-HEMTs versus advanced n-MOSFET in low drain voltage regime (few kT/q). In this low bias condition, figure of merits such as, fT are higher and intrinsic gate delay and energy are almost one order of magnitude lower in the case of III-V based-devices (two orders of magnitude for the delay-energy product).