High frequency properties of Si/SiGe n-MODFETs: dependence on gate length and temparture

The HF performances of n-type strained Si channel Modulation Doped Field Effect Transistors (MODFETs) with 0.118 µm, 0.130 µm and 0.250 µm gate lengths are reported at 300 K and 50 K. At 300K, intrinsic cut-off frequencies fTi are 65 GHz, 58 GHz, 37 GHz and maximum oscillation frequencies fMAX are 76 GHz ,60 GHz, and 100 GHz , respectively. The 0.130 µm device presents at 300 K a record intrinsic transconductance of 715 mS/mm and excellent noise performances with a de-embedded Minimum Noise Figure NFmin of 0.3 dB at 2.5 GHz. The variation of fMAX underlines the importance of the device parasitic resistances

Ultra thin gate oxide characterization

The increase of the gate leakage current of advanced CMOS technologies makes standard electrical characterization methods as C(V) measurement or charge pumping more complex and uncertain. In this paper, and based on C(V) characteristics, main elements that directly affect the electrical measurements of ultra thin MOS devices are clarified. Then, classical parameter extraction techniques are reviewed, pointing out their absolute limitations or giving potential keys of improvement

SiGe Hetero FETs on silicon at cryogenic temperature

Better transport properties and band gap engineering give a growing importance to SiGe alloy technologies in microelectronics. Transport properties, performances and potential of SiGe hetero FETs at cryogenic temperatures are reviewed focussing on RF and low noise

Strained silicon FETs on thin SiGe virtual substrates produced by He implantation: effect of reduced self-heating on DC and RF performance

Strained-Si based SiGe MODFETs on ultra-thin SiGe virtual substrates prepared by molecular beam epitaxy (MBE) and helium implantation are presented and compared to similar devices on thick, compositionally graded virtual substrates grown by low energy plasma enhanced CVD (LEPECVD). MBE grown 100 nm thick pseudomorphic Si0.67Ge0.33 layers have been relaxed to about 70% by using He+ ions implanted with a dose of 2 x 10(16) cm(-2) at an energy of 18 keV approximately 100 nm below the hetero-interface, followed by an annealing step at 850 degreesC for 600 s. Then another Si0.67Ge0.33 layer and a modulation doped strained Si QW are grown on top of the virtual substrate having a final degree of relaxation of about 80%. A cut-off frequency of f(max)(MAG) = 121 GHz was achieved with RF devices having a gate length of 70 nm. Self-heating effects in devices on thick, graded, and on thin buffer layers are addressed by experimental DC and RF data and 2-D numerical simulations of the device temperature. (C) 2004 Elsevier Ltd. All rights reserved

Self-reaction of HO2 and DO2: negative temperature dependence and pressure effects

The negative temperature dependence, pressure dependence, and isotope effects of the self-reaction of HO2 are modeled, using RRKM theory, by assuming that the reaction proceeds via a cyclic, hydrogen-bonded intermediate. The negative temperature dependence is due to a tight transition state, with a negative threshold energy relative to reactants, for decomposition of the intermediate to products. A symmetric structure for this transition state reproduces the observed isotope effect. The weak pressure dependence for DO2 self-reaction is due to the approach to the high-pressure limit. Addition of a polar collision partner, such as ammonia or water vapor, enhances the rate by forming an adduct that reacts to produce deexcited intermediate. A detailed model is presented to fit the data for these effects. Large ammonia concentrations should make it possible to reach the high-pressure limit of the self-reaction of HO2