| 41. |
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| 42. |
- Dey, Anil, et al.
(författare)
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Single InAs/GaSb Nanowire Low-Power CMOS Inverter
- 2012
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984.
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Tidskriftsartikel (refereegranskat)abstract
- III − V semiconductors have so far predom- inately been employed for n-type transistors in high-frequency applications. This development is based on the advantageous transport properties and the large variety of heterostructure combinations in the family of III − V semiconductors. In contrast, reports on p-type devices with high hole mobility suitable for complementary metal − oxide − semiconductor (CMOS) circuits for low-power operation are scarce. In addition, the di ffi culty to integrate both n- and p-type devices on the same substrate without the use of complex bu ff er layers has hampered the development of III − V based digital logic. Here, inverters fabricated from single n-InAs/p-GaSb hetero- structure nanowires are demonstrated in a simple processing scheme. Using undoped segments and aggressively scaled high- κ dielectric, enhancement mode operation suitable for digital logic is obtained for both types of transistors. State-of-the-art on- and o ff -state characteristics are obtained and the individual long-channel n- and p-type transistors exhibit minimum subthreshold swings of SS = 98 mV/dec and SS = 400 mV/dec, respectively, at V ds = 0.5 V. Inverter characteristics display a full signal swing and maximum gain of 10.5 with a small device-to-device variability. Complete inversion is measured at low frequencies although large parasitic capacitances deform the waveform at higher frequencies.
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| 43. |
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| 44. |
- Dick Thelander, Kimberly, et al.
(författare)
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Controlling the Abruptness of Axial Heterojunctions in III-V Nanowires: Beyond the Reservoir Effect
- 2012
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 12:6, s. 3200-3206
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Tidskriftsartikel (refereegranskat)abstract
- Heterostructure nanowires have many potential applications due to the avoidance of interface defects by lateral strain relaxation. However, most heterostructure semiconductor nanowires suffer from persistent interface compositional grading, normally attributed to the dissolution of growth species in the common alloy seed particles. Although progress has been made for some material systems, most binary material combinations remain problematic due to the interaction of growth species in the alloy. In this work we investigate the formation of interfaces in InAs-GaAs heterostructures experimentally and theoretically and demonstrate a technique to attain substantially sharper interfaces. We show that by pulsing the Ga source during heterojunction formation, In is pushed out before GaAs growth initiates, greatly reducing In carry-over. This procedure will be directly applicable to any nanowire system with finite nonideal solubility of growth species in the alloy seed particle and greatly improve the applicability of these structures in future devices.
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| 45. |
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| 46. |
- Dubrovskii, Vladimir G., et al.
(författare)
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Length Distributions of Nanowires Growing by Surface Diffusion
- 2016
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 16:4, s. 2167-2172
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Tidskriftsartikel (refereegranskat)abstract
- We present experimental data on the time and radius-dependent length distributions of Au-catalyzed InAs nanowires grown by metal organic vapor phase epitaxy. We show that these distributions are not as sharp as commonly believed. Rather, they appear to be much broader than Poissonian from the very beginning and spread quickly as the nanowires grow. We develop a model that attributes the observed broadening to the diffusion-induced character of growth. In the initial growth stage, the nanowires are fed from their entire length, leading to a Polya-like length distribution whose standard deviation is proportional to the mean length. After the nanowire length exceeds the adatom diffusion length, the growth acquires a Poissonian character in which the standard deviation scales as a square root of the mean length. We explain why wider nanowires have smaller length dispersion and speculate on the length distributions in Au-catalyzed versus self-catalyzed growth methods.
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| 47. |
- Egard, Mikael, et al.
(författare)
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60 GHz Wavelet Generator for Impulse Radio Applications
- 2009
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Ingår i: European Microwave Conference, 2009. EuMC 2009. - 9781424447480 ; , s. 1908-1911, s. 234-237
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Konferensbidrag (refereegranskat)abstract
- A wavelet generator producing 100 ps short pulses at 60 GHz is presented. The wavelet generator consists of a gated tunnel diode (GTD) integrated in parallel with an inductor. This forms a negative differential conductance (NDC) oscillator with the ability to switch the NDC property on and off, which makes it possible to generate short pulses. In the experiments described, the wavelet generator drives a 50 Omega load and delivers 206 mV(pp) when generating 97 ps short pulses at 60 GHz. It Is demonstrated that it is possible to generate pulses of different length and phase. An explanation of the almost instantaneously startup and decay lapse of the oscillator, including generation of signals with opposite phase, is presented. This novel circuit may find use in ultra-wideband impulse radio communication.
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| 48. |
- Egard, Mikael, et al.
(författare)
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Frequency Modulation in mm-Wave InGaAs MOSFET/RTD Wavelet Generators
- 2013
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Ingår i: 2013 International Conference on Indium Phosphide and Related Materials (IPRM). - 1092-8669. ; , s. 1-2
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Konferensbidrag (refereegranskat)abstract
- Co-integration of an InGaAs MOSFET and an RTD is performed to realize a wavelet generator. The large transconductance of the MOSFET (1.9 mS/mu m) is used to switch the current in an oscillator circuit and coherent wavelets down to 41 ps are generated in the frequency domain of 50 to 100 GHz. The lowest power consumption measured is 1.9 pJ/pulse. It is found that the supply bias can be used to modulate the center frequency of the wavelets.
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| 49. |
- Egard, Mikael, et al.
(författare)
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High-Frequency Performance of Self-Aligned Gate-Last Surface Channel In0.53Ga0.47As MOSFET
- 2012
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Ingår i: IEEE Electron Device Letters. - 0741-3106. ; 33:3, s. 369-371
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a self-aligned L-g = 55 nm In-0.53 Ga-0.47 As MOSFET incorporating metal-organic chemical vapor deposition regrown n(++) In0.6Ga0.4As source and drain regions, which enables a record low on-resistance of 199 Omega mu m. The regrowth process includes an InP support layer, which is later removed selectively to the n(++) contact layer. This process forms a high-frequency compatible device using a low-complexity fabrication scheme. We report on high-frequency measurements showing f(max) of 292 GHz and f(t) of 244 GHz. These results are accompanied by modeling of the device, which accounts for the frequency response of gate oxide border traps and impact ionization phenomenon found in narrow band gap FETs. The device also shows a high drive current of 2.0 mA/mu m and a high extrinsic transconductance of 1.9 mS/mu m. These excellent properties are attributed to the use of a gate-last process, which does not include high temperature or dry-etch processes.
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| 50. |
- Egard, Mikael, et al.
(författare)
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High Transconductance Self-Aligned Gate-Last Surface Channel In0.53Ga0.47As MOSFET
- 2011
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Ingår i: 2011 IEEE International Electron Devices Meeting (IEDM). - 9781457705052
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Konferensbidrag (refereegranskat)abstract
- In this paper we present a 55 nm gate length In0.53Ga0.47As MOSFET with extrinsic transconductance of 1.9 mS/mu m and on-resistance of 199 Omega mu m. T he self-aligned MOSFET is formed using metalorganic chemical vapor deposition regrowth of highly doped source and drain access regions. The fabricated 140 nm gate length devices shows a low subthreshold swing of 79 mV/decade, which is attributed to the described low temperature gate-last process scheme.
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