Remote phonon and surface roughness limited universal electron mobility of In0.53Ga0.47As surface channel MOSFETs

The inversion layer electron mobility in n-channel In_0.53Ga_0.47As MOSFET’s with HfO₂ gate dielectric with several substrate impurity concentrations (∼1 × 10¹⁶ cm⁻³ to ∼1 × 10¹⁸ cm⁻³) and various surface preparations (HF surface clean, (NH₄)₂S surface clean and PECVD a-Si interlayer with a HfO₂ gate dielectric) have been studied. The peak electron mobility is observed to be strongly dependent on the surface preparation, but the high field mobility is observed to be almost independent of the surface preparation. A detailed analysis of the effective mobility as a function of electric field, substrate doping, and temperature was used to determine the various mobility components (surface roughness, phonon, and coulombic scattering limited mobility components). For the substrates with high doping concentration, the electron mobility at low vertical electric field is dominated by Coulomb scattering from the substrate dopants, whereas, for lower substrate doping the Coulombic scattering is dominated by the disorder induced gap states. Low temperature measurements were used to determine the surface roughness scattering and phonon components. The results show that room temperature mobility of In_0.53Ga_0.47As surface channel MOSFETs with HfO₂ gate dielectric at high electric field is limited primarily by remote phonons whereas the Al₂O₃ gate dielectric is limited by surface roughness scattering.     

The structural and electrical properties of the SrTa2O6/In0.53Ga0.47As/InP system

The structural and electrical properties of SrTa₂O₆(SrTaO)/n-In_0.53GaAs_0.47(InGaAs)/InP structures where the SrTaO was grown by atomic vapor deposition, were investigated. Transmission electron microscopy revealed a uniform, amorphous SrTaO film having an atomically flat interface with the InGaAs substrate with a SrTaO film thickness of 11.2 nm. The amorphous SrTaO films (11.2 nm) exhibit a dielectric constant of ∼20, and a breakdown field of >8 MV/cm. A capacitance equivalent thickness of ∼1 nm is obtained for a SrTaO thickness of 3.4 nm, demonstrating the scaling potential of the SrTaO/InGaAs MOS system. Thinner SrTaO films (3.4 nm) exhibited increased non-uniformity in thickness. From the capacitance-voltage response of the SrTaO (3.4 nm)/n-InGaAs/InP structure, prior to any post deposition annealing, a peak interface state density of ∼2.3 × 10¹³ cm⁻² eV⁻¹ is obtained located at ∼0.28 eV (±0.05 eV) above the valence band energy (E_v) and the integrated interface state density in range E_v + 0.2 to E_v + 0.7 eV is 6.8 × 10¹² cm⁻². The peak energy position (0.28 ± 0.05 eV) and the energy distribution of the interface states are similar to other high-k layers on InGaAs, such as Al₂O₃ and LaAlO₃, providing further evidence that the interface defects in the high-k/InGaAs system are intrinsic defects related to the InGaAs surface.     

Silicon and selenium implantation and activation in In0.53Ga0.47As under low thermal budget conditions

Si and Se implantations have been systematically investigated in In_0.53Ga_0.47As. Different implant doses and various activation anneals with temperatures up to 700 °C have been examined. Raising Si implant dose from 1 × 10¹⁴ to 1 × 10¹⁵ cm⁻² was found to increase the active doping concentration by about a factor of two. As confirmed by Transmission Electron Microscopy (TEM) and electrical measurements, the rest of the implanted Si ions remain as defects in the crystal and degrade the mobility. It was also confirmed from Secondary Ion Mass Spectrometry (SIMS) that the Si diffusivity in InGaAs is negligible up to 700 °C implant activation anneal making Si a suitable option for the formation of shallow junctions in InGaAs. The activation efficiency, sheet resistance, carrier density and mobility data of 25 keV Se and Si implanted InGaAs layers are also presented under various activation anneal temperatures.     

Effects of high doping on the bandgap bowing for AlxGa1−xN

This paper gives the composition dependence of the bandgap energy for highly doped n-type Al_xGa_1−xN. We report results of the bowing parameter obtained using a random simulation. Three groups of Al_xGa_1−xN semiconductors were considered and which are distinguishable by their non degenerate or degenerate character in the doping density (10¹⁷?N_D?10²⁰ cm⁻³). A striking feature is the large discrepancy of the bandgap bowing (−2.02?b?2.94 eV), as was demonstrated from our calculations. This suggests that high doping may be a possible cause able to induce the large range of bowing parameters reported for Al_xGa_1−xN alloys.     

High electron mobility 18300 cm2/V·s in the InAIAs/lnGaAs pseudomorphic structure obtained by channel indium composition modulation

The highest electron mobility yet reported for an InP-based pseudomorphic structure at room temperature, 18300 cm²/V·s, has been obtained by using a structure with an indium composition modulated channel, namely, In_0.53Ga_0.47As/ In_0.8Ga_0.2As/InAs/In_0.8Ga_0.2As/In_0.53Ga_0.47As. Although the total thickness of the high In-content layers (In_0.8Ga_0.2As/InAs/In_0.8Ga_0.2As) exceeds the critical thick-ness predicted by Matthews theory, In_0.8Ga_0.2As insertion makes it possible to form smooth In_0.53Ga_0.47As/In_0.8Ga_0.2As and In_0.8Ga_0.2As/InAs heterointerfaces. This structure can successfully enhance carrier confinement in the high In-content layers. This superior carrier confinement can be expected to lead to the highest yet reported electron mobility.     

New low contact resistance triple capping layer enabling very high Gm InAIAs/lnGaAs HEMTs

It has been demonstrated that a highly doped (Si:3 × 10¹⁹ cm^-3) triple capping layer consisting of n⁺−In_0.53Ga_0.47As, n⁺−In_0.52Al_0.48As, and n⁺-In_0.53Ga_0.47As can remarkably reduce the parasitic source resistance in InP-based high electron mobility transistors (HEMTs). The analysis of the source resistance revealed that the resistance element at the n⁺−In_0.53Ga_0.47As/un−In_0.52Al_0.48As/un-In_0.53Ga_0.47As channel heterointerfaces was as large as 70% of the source resis-tance when nonalloyed ohmic electrodes were used. The highly doped triple capping layer reduces the resistance contribution of vertical conduction between the capping layer and 2DEG channel. A low source resistance of 0.57 Ωmm and a low contact resistivity of 3 × 10⁻⁵ Ωcm² were obtained for the HEMTs with the highly doped triple capping layer, which were 60% lower and one order of magnitude smaller than those for the HEMTs with a conventional single capping layer doped 5 × 10¹⁸ cm⁻³, respectively. These values were also 70 and 30% lower than those for the HEMTs with a highly doped (3 × 10¹⁹ cm⁻³) single capping layer, respectively. The low source resistance brings high peak extrinsic transconduc-tance of 1 S/mm for a device with 0.4 μm long gate, which was 42% higher than the previously reported HEMTs with the same gate length.     

The study of δ-doped InGaP/InGaAs/GaAs pseudomorphic high electron mobility transistor

An enhancement-mode pseudomorphic high electron mobility transistor (E-mode pHEMT) with In_0.49Ga_0.51P/In_0.25Ga_0.75As/GaAs structure is studied in this paper. The two-dimensional device simulator, MEDICI, is used to solve the Poisson's equation and the electron/hole current continuity equations. An optimized δ-doped InGaP/InGaAs pHEMT structure is found to be superior to the conventional AlGaAs/InGaAs pHEMT. It reveals that the maximum drain-source current (I_DS) goes up to 1600 mA/mm and transconductance (G_m) is 2120 mS/mm.     

20-nm enhancement-mode metamorphic GaAs HEMT with highly doped InGaAs source/drain regions for high-frequency applications

In this article, the DC and RF performance of a SiN passivated 20-nm gate length metamorphic high electron mobility transistor (MHEMT) on GaAs substrate with highly doped InGaAs source/drain (S/D) regions have investigated using the Synopsys TCAD tool. The 20-nm enhancement-mode (E-mode) MHEMT device also features δ-doped sheets on either side of the In_0.53Ga_0.47As/InAs/In_0.53Ga_0.47As channel which exhibits a transconductance of 3100 mS/mm, cut-off frequency (f_T) of 740 GHz and a maximum oscillation frequency (f_max) of 1040 GHz. The threshold voltage of the device is found to be 0.07 V. The room temperature Hall mobilities of the 2-dimensional sheet charge density are measured to be over 12,600 cm²/Vs with a sheet charge density larger than 3.6 × 10¹² cm^?2. These high-performance E-mode MHEMTs are attractive candidates for sub-millimetre wave applications such as high-resolution radars for space research, remote atmospheric sensing, imaging systems and also for low noise wide bandwidth amplifier for future communication systems.     

Investigation of graded InxGa1−xP buffer by Raman scattering method

The compositional changes of In_xGa_1−xP graded buffer inserted between GaP substrate and subsequently grown In_0.36Ga_0.64P homojunction LED structure were investigated by Raman spectroscopy. The indium content of In_xGa_1−xP interlayers was increased in eight steps with thickness of 300 nm and constant compositional change Δx_In between the steps. The properties of In_xGa_1−xP graded buffer along the structure cross-section have been studied by Raman back scattering method and the changes in GaP LO and TO phonons were investigated. Raman shift of 13 cm⁻¹ in GaP-like LO₁ phonon was measured on beveled [100]surface for compositional change of In_xGa_1−xP layer in the range of 0<x_In<0.32. The measurements on the cleaved edge of the sample in [011] direction revealed a strong TO phonon at 366 cm⁻¹ and weak LO phonon peak at 405 cm⁻¹ in GaP substrate. By reaching the graded In_xGa_1−xP region the intensity of TO phonon decreases and appearance of considerable TO₁ phonon shift up to 350 cm⁻¹ for In content x_In=0.16 was observed. For upper graded layers with x_In from 0.16 to 0.24 the position of GaP-like TO₁ was constant and can be ascribed to relaxation of lattice mismatched thin In_xGa_1−xP graded upper layers in the structure.     

OMVPE growth of In0.53Ga0.47As on InP using tertiarybutylarsine

We have successfully grown bulk In_0.53Ga_0.47As on InP using tertiarybutylarsine (TBA), trimethylindium and trimethylgallium. The growth temperature was 602° and the V/III ratio ranged from 19 to 38. Net carrier concentrations were 2 – 4 × 10¹⁵ cm^-3, n-type, with a peak 77 K mobility of 68,000 cm²/V. sec. Increasing compensation was observed in In_0.53Ga_0.47As grown at higher V/III ratios. PL spectra taken at 5 K revealed strong near bandgap emission at 0.81 eV—with the best sample having a FWHM of 2.5 meV. At lower energies, donor-acceptor pair transitions were evident. Strong and sharp 5 K PL emission was observed from InP/In_0.53Ga_0.47As/InP quantum wells grown with TBA.     

Electron transport in an In<Subscript>0.52</Subscript>Al<Subscript>0.48</Subscript>As/In<Subscript>0.53</Subscript>Ga<Subscript>0.47</Subscript>As/In<Subscript>0.52</Subscript>Al<Subscript>0.48</Subscript>As quantum well with a δ-Si doped barrier in high electric fields

The electron conduction in a two-dimensional channel of an In_0.52Al_0.48As/In_0.53Ga_0.47As/In_0.52Al_0.48As quantum well (QW) with a δ-Si doped barrier has been investigated. It is shown that the introduction of thin InAs barriers into the QW reduces the electron scattering rate from the polar optical and interface phonons localized in the QW and increases the electron mobility. It is found experimentally that the saturation of the conduction current in the In_0.53Ga_0.47As channel in strong electric fields is determined by not only the sublinear field dependence of the electron drift velocity, but also by the decrease in the electron concentration n _s with an increase in the voltage across the channel. The dependence of n _s on the applied voltage is due to the ionized-donor layer located within the δ-Si doped In_0.52Al_0.48As barrier and oriented parallel to the In_0.53Ga_0.47As QW.     

Optimization of sub-0.1-μm offset Γ-shaped gate MHEMTs for millimeter-wave applications

We examine the effects of device scaling in both vertical and lateral dimensions for the metamorphic high electron mobility transistors (MHEMTs) on the DC and millimeter-wave electrical performances by using a hydrodynamic transport model. The well-calibrated hydrodynamic simulation for the sub-0.1-μm offset Γ-gate In_0.53Ga_0.47As/In_0.52Al_0.48As MHEMTs shows a reasonable agreement with the electrical characteristics measured from the fabricated 0.1 μm devices. We have calibrated all the parameters using the measurement data with various physical considerations to take into account the sophisticated carrier transport physics in sub-0.1-μm devices. Being simulated with these calibrated parameters, the optimum device performance is obtained at a source-drain spacing of 2 μm, a gate length of 0.05 μm, a barrier thickness of 10 nm and a channel thickness of 12 nm.     

High-mobility pentacene thin-film transistor by using LaxTa(1−x)Oy as gate dielectric

Pentacene organic thin-film transistors (OTFTs) using La_xTa_(1−x)O_y as gate dielectric with different La contents (x = 0.227, 0.562, 0.764, 0.883) have been fabricated and compared with those using Ta oxide or La oxide. The OTFT with La_0.764Ta_0.236O_y can achieve a carrier mobility of 1.21 cm² V⁻¹s⁻¹s, which is about 40 times and two times higher than those of the devices using Ta oxide and La oxide, respectively. As supported by XPS, AFM and noise measurement, the reasons lie in that La incorporation can suppress the formation of oxygen vacancies in Ta oxide, and Ta content can alleviate the hygroscopicity of La oxide, resulting in more passivated and smoother dielectric surface and thus larger pentacene grains, which lead to higher carrier mobility.     

Proton bombardment in n- and p-type Ga0.47In0.53As

Ga_0.47In_0.53As epitaxial layers on InP substrate have been subjected to proton bombardment. The resistivity increases up to 10⁴Ω cm for 10¹⁴H⁺/cm² in p-type and 3 · 10¹⁶H⁺/cm² in n-type a_0.47In_0.53As implanted at 77 K. Proton bombardment at 300 K showed this increase in resistivity only for p-type material. Channeling experiments indicated that the damage of the lattice which seems to be responsible for the resistivity increase of n-material can be produced only at low temperature with doses of the order of 10¹⁶H⁺/cm². Crystalline layers implanted with high dose showed blistering effects after heat treatments.     

Zinc diffusion in InAsP/InGaAs heterostructures

A systematic study of the sealed ampoule diffusion of zinc into epitaxially grown InP, In_0.53Ga_0.47As, In_0.70Ga_0.30As, In_0.82Ga_0.18As, and through the InAsP/InGaAs interface is presented. Diffusion depths were measured using cleave-and-stain techniques, electrochemical profiling, and secondary ion mass spectroscopy. The diffusion coefficients, , were derived. For InP, D₀=4.82 × 10⁻²cm²/sec and E_a=1.63 eV and for In_0.53Ga_0.47As, D₀=2.02 × 10⁴cm²/sec and E_a=2.63 eV. Diffusion into the heteroepitaxial structures used in the fabrication of planar PIN photodiodes is dominated by the effects of the InP/InGaAs interface.     

Very high purity In0.53Ga0.47As grown by molecular beam epitaxy

Very high purity In0_0.53Ga_0.47As layers were grown by molecular beam epitaxy (MBE). Origins ofn-type impurities in undoped In_0.53Ga_0.47As grown on an InP:Fe substrate were systematically examined. The most possible origins were impurities diffusing from the InP:Fe substrate and those contained in As molecular beam. These impurities were dramatically reduced by using an InAlAs buffer layer and a growth condition of high substrate temperature and low As pressure. The lowest electron concentration of the In0_0.53Ga_0.47As layer wasn = 1.8 × 10¹³ cm_-3 with mobilitiesμ = 15200 cm²/Vs at 300 K andμ = 104000 cm²/Vs at 77 K.     

Interface optimization using diindenoperylene for C60 thin film transistors with high electron mobility and stability

C₆₀-based organic thin film transistors (OTFTs) with high electron mobility and high operational stability are achieved with (1 1 1) oriented C₆₀ films grown by using template effects of diindenoperylene (DIP) under layer on the SiO₂ gate insulator. The electron mobility of the C₆₀ transistor is significantly increased from 0.21 cm² V⁻¹ s⁻¹ to 2.92 cm² V⁻¹ s⁻¹ by inserting the template-DIP layer. Moreover much higher operational stability is also observed for the DIP-template C₆₀ OTFTs. A grazing incidence X-ray diffraction and ultrahigh-sensitivity photoelectron spectroscopy measurements indicate that the improved electron mobility and stability arise from the decreased density of trap states in the C₆₀ film due to increased (1 1 1) orientation of C₆₀-grains and their crystallinity on the DIP template.     

Study of Shubnikov-de Haas oscillations and measurement of hole effective mass in compressively strained InXGa1−XSb quantum wells

In_XGa_1−XSb has the highest hole mobility amongst all III-V semiconductors which can be enhanced further with the use of strain. The use of confinement and strain in In_XGa_1−XSb quantum wells lifts the degeneracy between the light and heavy hole bands which leads to reduction in the hole effective mass in the lowest occupied band and an increase in the mobility. We present magnetotransport measurements on compressively strained In_XGa_1−XSb and GaSb quantum wells. Hall-bar and Van de Pauw structures were fabricated and Shubnikov-de Haas oscillations in the temperature range of T = 2-10 K for magnetic fields of B = 0-9 T were measured. The reduction of effective hole mass with strain was quantified. These results are in excellent agreement with modeling results from band structure calculations of the effective hole mass in the presence of strain and confinement.     

高峰谷电流比的高掺杂发射区In0.53Ga0.47As/AlAs共振隧穿二极管

利用空气桥工艺设计和制作了高掺杂发射区In0.53Ga0.47As/AlAs共振隧穿二极管（RTD）。在室温下,器件的峰谷电流比大于40,峰值电流密度为24kA/cm2。建立了RTD器件等效电路模型,并从直流和微波测试结果中提取出器件参数。高峰谷电流比的RTD器件具有非常小的电容,有利于在微波/太赫兹领域中的应用。