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1.
Graded‐base InGaAs/InP HBTs were passivated by (NH4)2S solution. The current gain increased after passivation. A current gain degradation was found when the passivated HBT was exposed to air. The Gummel plots in forward and reverse modes were used to evaluate the properties of the base–emitter and base–collector junctions. The degradations of the base–emitter and base–collector junctions were found to be different. The current gain was independent on the emitter size after passivation compared to the emitter size dependent one before passivation. The size dependent current gain appeared when HBTs exposed to air for 10 days. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
2.
Deep level transient spectroscopy (DLTS) and high-frequency capacitance-voltage (HF-CV) measurement are used for the investigation of HfAlO/p-Si interface. The so-called “slow” interface states detected by HF-CV are obtained to be 2.68 × 1011 cm−2. Combined conventional DLTS with insufficient-filling DLTS (IF-DLTS), the true energy level position of interfacial traps is found to be 0.33 eV above the valance band maximum of silicon, and the density of such “fast” interfacial traps is 1.91 × 1012 cm−2 eV−1. The variation of energy level position of such traps with different annealing temperatures indicates the origin of these traps may be the oxide-related traps very close to the HfAlO/Si interface. The interfacial traps’ passivation and depassivation effect of postannealing in forming gas are shown by comparing samples annealed at different temperatures. 相似文献
3.
S. A. Vitusevich M. V. Petrychuk S. V. Danylyuk A. M. Kurakin N. Klein A. E. Belyaev 《physica status solidi (a)》2005,202(5):816-819
We investigated low‐frequency noise in passivated and nonpassivated AlGaN/GaN high electron mobility transistor (HEMT) heterostructures grown on SiC substrate. The heterostructure layers are grown without intentionally doping the barrier material and two‐dimensional gas appears at the interface only due to polarization effects. Transmission line model structures with different lengths of the conducting channel were studied in a wide range of temperatures in a linear regime. The magnitude of the noise and Hooge parameter demonstrate different dependence on the distance between contacts in passivated and non‐passivated structures. Noise reduction in the structure for around one order of magnitude after passivation was revealed and different origins of the noise before and after passivation established. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
The built‐in electric field applied at the cubic GaN/GaAs(001) heterointerfaces and its evolution during the growth process were evaluated using a phase‐selected photoreflectance technique in combination with a variable‐wavelength excitation light, to clarify the origin of the higher‐electric‐field signal observed in the previous photoreflectance study. The spectrum from LT‐GaN/GaAs after 900 °C annealing contains a extremely‐slow signal with a high electric‐field strength and this signal became dominant with decreasing the penetration depth of the modulating light. This confirms the presence of a triangular well just beneath the GaN/GaAs interface regarding the direction of the band‐bending investigated by the previous work, which can be attributed to the parallel‐conduction path ideal for the holes to drift through. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
J. A. Wilson M. MacKenzie S. MacFadzean T. McMullen S. Hamill P. Stopford M. C. Holland C. R. Stanley A. R. Long 《physica status solidi (a)》2006,203(3):628-637
Measurements of the electron transport properties in Inx Ga1−x As (x = 0.2 and x = 0.3) channel heterostructures have consistently shown the transport mobility to be higher in the [01&1macr;] direction compared to [011] on a (100) wafer. Low temperature (1.6 K) measurements of these materials show that the mobility difference can be as large as 30% whilst the differences in carrier concentrations for the two directions are negligible in comparison. The mobility anisotropy decreases to below 5% at room temperature as the effects of phonon scattering, which is isotropic, begin to dominate. The anisotropy in the quantum mobility is much less pronounced than that in the transport mobility. This suggests that the low mobility in the [011] direction is primarily a result of large angle scattering. Transmission electron microscopy (TEM) analysis was performed on cross‐sections of material in the two directions. Thickness fluctuations in the channel were observed whilst traversing the channel of a (01&1macr;) section in the [011] direction where as none were observed in (011) sections along the [01&1macr;] direction. The length scale of the fluctuations was variable but typically around 50–100 nm. Transport simulations reveal that a 1‐dimensional potential modulation with a wavelength similar to that of the fluctuations produces a mobility anisotropy with the observed sign. Therefore it is likely that the thickness variations, possibly combined with synchronous fluctuations in the indium concentration along the [011] direction, are responsible for the reduced mobility in [011] transport. Although to the best of our knowledge these thickness fluctuations are reported here for the first time, similar growth anisotropies are well known for Inx Ga1−x As layers deposited on InP. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
Masahiko Kuraguchi Yoshiharu Takada Takashi Suzuki Mayumi Hirose Kunio Tsuda Wataru Saito Yasunobu Saito Ichiro Omura 《physica status solidi (a)》2007,204(6):2010-2013
A new device structure with four epitaxial layers and a recessed gate is proposed for normally‐off operation in GaN‐FETs. Employment of this structure makes it possible to control accurately the threshold voltage without accurate control of recess etching depth. The high breakdown voltage and the low on‐resistance of the fabricated devices are also reported. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
7.
A Physics-Based Compact Direct-Current and Alternating-Current Model for AlGaN/GaN High Electron Mobility Transistors 
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下载免费PDF全文 A set of analytical models for the dc and small signal characteristics of AIGaN/GaN high electron mobility transis- tors （HEMTs） are presented. A modified transferred-electron mobility model is adapted and a phenomenological low-field mobility model is developed. We calculate the channel charge considering the neutralization of donors and the contribution of free electrons in the AlGaN layer. The gate-to-source and gate-to-drain capacitances are obtained analytically, and the cut-off frequency is predicted. The models are implemented into the HSPICE simulator for the dc, ac and transient simulations and verified by experimental data for the first time. A high efficiency class-E GaN HEMT power amplifier is designed and simulated by the HSPICE to verify the applicability of our models. 相似文献
8.
This paper attempts to realize unpinned high-k insulator-semiconductor interfaces on air-exposed GaAs and In0.53Ga0.47As by using the Si interface control layer (Si ICL). Al2O3 was deposited by ex situ atomic layer deposition (ALD) as the high-k insulator. By applying an optimal chemical treatment using HF acid combined with subsequent thermal cleaning below 500 °C in UHV, interface bonding configurations similar to those by in situ UHV process were achieved both for GaAs and InGaAs after MBE growth of the Si ICL with no trace of residual native oxide components. As compared with the MIS structures without Si ICL, insertion of Si ICL improved the electrical interface quality, a great deal both for GaAs and InGaAs, reducing frequency dispersion of capacitance, hysteresis effects and interface state density (Dit). A minimum value of Dit of 2 × 1011 eV−1 cm−2 was achieved both for GaAs and InGaAs. However, the range of bias-induced surface potential excursion within the band gap was different, making formation of electron layer by surface inversion possible in InGaAs, but not possible in GaAs. The difference was explained by the disorder induced gap state (DIGS) model. 相似文献
9.
A. A. Klochikhin V. Yu. Davydov I. Yu. Strashkova P. N. Brunkov A. A. Gutkin M. E. Rudinsky H.‐Y. Chen S. Gwo 《固体物理学:研究快报》2007,1(4):159-161
The exact solution of the Thomas–Fermi equation for a planar accumulation layer of a degenerate semiconductor is presented. The obtained results are compared with theoretical literature data. The applicability of the solution is demonstrated by using results of electrochemical capacitance–voltage measurements and photoluminescence data for n‐InN epilayers. It has been found that the difference between the electron concentrations estimated from the Hall and photoluminescence measurements is a measure of the electron content in the accumulation layer with acceptable accuracy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
10.
T. Palacios L. Shen S. Keller A. Chakraborty S. Heikman D. Buttari S. P. DenBaars U. K. Mishra 《physica status solidi (a)》2005,202(5):837-840
A new kind of high electron mobility transistor (HEMT) based on a GaN‐spacer is reported. To confine the two‐dimensional electron gas in this AlGaN‐free HEMT, a GaN/ultrathin AlN/GaN pseudo‐hetero‐junction has been used. The effective conduction band discontinuity is given by the AlN polarization‐induced electric field. This new transistor shows a superior general performance than the standard HEMT due to a decrease in the alloy and real space transfer scattering, as well as lower ohmic contact resistance. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
11.
We have fabricated Pnp AlGaN/GaN heterojunction bipolar transistors and investigated their common‐emitter current–voltage (I–V) characteristics at the temperatures from room temperature to 300 °C. Good saturation properties were observed in their common‐emitter I–V characteristics. The current gain of 20 at room temperature increased with elevating the temperature. The maximum current gain was as high as 71 at 300 °C with the collector current from 20 to 200 μA. This increase in current gain is ascribed to the enhancement in the hole injection efficiency from the p‐AlGaN emitter to the n‐GaN base as well as the reduction of the device resistance and the improved Ohmic characteristics of the subcollector. These results indicate that Pnp HBTs have the potential for high temperature operation. 相似文献
12.
Tomas Palacios 《physica status solidi (a)》2009,206(6):1145-1148
Solid state power amplifiers operating at mm‐ and sub‐mm‐wave frequencies are key components of numerous communication, sensors and defense systems. Nitride semiconductors have the potential to provide unprecedented levels of power at these frequencies. However, a multidimensional design and optimization is required to achieve acceptable levels of power gain and efficiency at high frequencies. In this paper we discuss some of the main challenges to increase the operating frequency of nitride transistors. New solutions are proposed to increase the electron confinement, electron velocity and access resistances of deeply scaled devices (Abstract figure) and to unleash their great potential. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
In this work we analyze the effect of (NH)2Sx wet treatment on the GaAs(1 0 0) covered with “epiready” oxide layer without any pretreatment in order to check the removal of oxides and carbon-related contamination, and the formation of sulfur species. The sulfidation procedure consisted of epiready sample dipping (at room and 40 °C temperatures) in an ammonium polysulfide solution combined with a UHV flash annealing up to 500 °C.The inspection of the XPS As 2p3/2 and Ga 2p3/2 spectra taken at surface sensitive mode revealed: (i) the temperature-dependent reduction of the amount of GaAs oxides and carbon contamination after sulfidation, and almost their complete removal after subsequent annealing, (ii) the creation of sulfur bonds with both Ga and As, with more thermally stable Ga-S bonds, and (iii) the slight reduction in elemental arsenic amount. 相似文献
14.
High‐frequency measurements of AlGaN/GaN HEMTs (high electron mobility transistors) with 1.3 μm long gate have been performed at temperatures between 23 and 187 °C. The cut‐off frequency fT decreased monotonically with increasing temperature. It was 13.7 and 8.7 GHz at 23 and 187 °C, respectively. The effective electron velocities veff in the channel, evaluated from the relation of total delay time versus the ID‐inverse, were 1.2 × 107 and 0.8 × 107 cm/s at 23 and 187 °C, respectively. It has been shown that the present device is in an intermediate state between mobility‐dominant and peak‐velocity‐dominant operations. 相似文献
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16.
A. Link T. Graf O. Ambacher A. Jimenez E. Calleja Y. Smorchkova J. Speck U. Mishra M. Stutzmann 《physica status solidi b》2002,234(3):805-809
To study the electronic transport properties of two‐dimensional electron gases confined at the interfaces of AlGaN/GaN heterostructures, Shubnikov–de Haas (SdH) and Hall measurements were performed with structures covering a wide range of sheet carrier concentrations from 2.25 × 1012 to 1.83 × 1013 cm—2. For samples with sheet carrier concentrations above 1.7 × 1013 cm—2, the occupation of a second subband was observed. Fourier transformation was used to separate the contributions of both occupied subbands to the electronic transport. Quite similar quantum scattering times and effective masses of the electrons in the first and second subband were determined. In samples with lower sheet carrier concentration traces of a spin splitting could be found by investigating the angle dependence of the SdH‐oscillations. 相似文献
17.
J. Kuzmik J.‐F. Carlin M. Gonschorek A. Kostopoulos G. Konstantinidis G. Pozzovivo S. Golka A. Georgakilas N. Grandjean G. Strasser D. Pogany 《physica status solidi (a)》2007,204(6):2019-2022
Gate and drain‐lag effects are studied in (GaN)/InAlN/GaN and InAlN/AlN/GaN HEMTs grown on sapphire. Electron trapping on the surface states between the gate and the drain forming the net negative charge up‐to ∼2 × 1013 cm–2 is found to be responsible for the gate‐lag effect in the (GaN)/InAlN/GaN HEMTs. If the polarization charge at the device surface is decreased by GaN capping, then density of the trapped charge is not changed, however the electron de‐trapping process becomes faster. The drain‐lag effect is caused by electron injection and trapping in the source‐gate area reaching ∼1 × 1013 cm–2 of the trapped charge in the steady state. In the studied voltage range the InAlN/AlN/GaN HEMT is shown to be gate‐lag‐free suggesting that this parasitic transient can be avoided if thin AlN is used in the epi‐layer growth sequence. It is assumed that this breakthrough quality relates to the decreased or even reverted electric field in the InAlN layer if AlN is inserted. Surface states need not to be generated in this case. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
18.
Trapping effects in AlGaN/GaN high‐electron mobility transistors (HEMTs) are investigated using dynamic current–voltage (I–V) measurements with different quiescent biases and pulse widths to examine post‐annealing effects after Schottky gate formation. The results show that trapping/detrapping phenomena by traps with emission/capture time constants of shorter than 10 µs are dominant in non‐annealed devices. The devices annealed at 400 °C for 10 minutes in a furnace exhibit significantly smaller current dispersion and have a smaller number of traps. However, after post‐annealing, a small number of traps with a time constant of longer than 10 µs are created or activated. Further annealing at 400 °C leads to increase in current dispersion, indicating that more traps with an emission time constant >10 ms are created. These traps induced by post‐annealing are responsible for the trapping effects when pulse width ≥10 µs. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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A numerical analysis of the stationary current–voltage characteristic of a p–i–n diode comprising a layer of self‐organized quantum dots is presented. For bias voltages below the flat band condition the current is given by sequential tunneling of holes and electrons in the quantum dots and the wetting layer. Their recombination causes a current through the device which shows well‐pronounced differential conductance oscillations. As a fingerprint of many‐particle charging effects in individual quantum dots we discuss these oscillations in terms of the strength of the Coulomb interaction between carriers in different quantum dots and the influence of the size distribution of the quantum dots. 相似文献