Hooge fluctuation parameter of semiconductor microstructures

The Hooge 1/f fluctuation parameter α_H of a mesoscopic n-GaAs filament is studied experimentally and compared with that derived from the quantum model. The minimum value of the Hooge parameter α_H was 2×10^-6 and 1×10 ^-8 at room temperature and 60 K, respectively. The temperature dependence of α_H below 100 K and the electric field dependence at 77 K are favorably compared with those obtained for the impurity scattering fluctuation of the quantum 1/f noise theory     

Temperature dependence of the Hooge parameter in n-channel Silicon JFET's

The Hooge noise parameter αHof n-channel Si-JFET's was measured as a function of temperature between 250 and 400 K. The data are in full agreement with an earlier heuristic quantum1/fnoise expression introduced by van der Ziel et al. and based on Handel's quantum1/fnoise theory.     

Improving InAs double heterostructure lasers with betterconfinement

The authors have conducted a theoretical study of InAs double heterostructure lasers. Carrier leakage due to drift current is shown to be the main mechanism of the injected carriers in lasers fabricated to date. Reduction of carrier leakage is shown to be possible by using wider bandgap lattice-matched material as the cladding layers. Increased optical confinement is also required to achieve the lowest possible threshold current, which strongly affects the highest lasing temperature achievable. An InAs double heterostructure employing AlAs_0.16Sb_0.84 as the cladding material is proposed. Simulation on this structure indicates that its threshold current density will be dominated by Auger recombination for most of the temperature range below 300 K, the estimated highest lasing temperature     

On the temperature dependence of the 1/f noise Hooge parameter αHin n-channel Silicon JFET's

It is suggested that the temperature dependence of the empirical Hooge noise parameter αHdeduced from recent noise measurements on n-channel Si-JFET's can be described asalpha_{H} propto exp (-T_{0}/T)whereT_{0} = 510 pm 130K. The characteristic exponent might be correlated with the energy of the low-wavenumber phonons dominating the mobility through intervalley scattering.     

Two-color luminescence from a single type-II InAsSbP/InAs heterostructure

Gradient scanning Kelvin-probe microscopy has been for the first time used to study p-n hetero-junctions based on narrow-gap compounds in the In-As-Sb-P solid-solution system. Redistribution of the flow of injected carriers in the sample along the direction of the external electric field is demonstrated for the example of a single type-II p-InAsSbP/n-InAs heterostructure. When a forward bias is applied to the hetero-structure, two-band luminescence is observed, i.e., that of the interface type at the p-InAsSbP/p-InAs heterointerface and of the bulk type in indium arsenide. It is shown that indirect (interface) transitions exhibit a higher radiative-recombination efficiency than direct interband transitions. The observation of multiband electroluminescence spectra opens up a means of developing single-heterostructure multicolored light-emitting diodes for the mid-IR spectral range (3–5 μm).     

A complementary heterostructure field effect transistor technologybased on InAs/AlSb/GaSb

A complementary heterojunction field effect transistor technology based on the InAs/AlSb/GaSb system is proposed. The structure is formed by the vertical integration of InAs n-channel and GaSb p-channel HFET devices. The superior transport properties of electrons in InAs and holes in GaSb and their band offsets to AlSb or AlSbAs yield devices with transconductances much greater than AlGaAs/GaAs n- and p-channel HFETs. It is shown that a complementary circuit fabricated from these devices could provide room-temperature performance up to six times greater than that predicted for AlGaAs/GaAs complementary circuits     

Hooge parameter of InGaAs bulk material and InGaAs 2DEG quantum well structures based on InP substrates

The 1/f noise of various InGaAs layers lattice matched to InP is investigated systematically at room temperature. To elucidate the origin of the 1/f noise in this type of III–V compound semiconductor, thick n-type doped InGaAs layers, typical InP based InAlAs/InGaAs or InP/InGaAs heterostrucuture field-effect transistor (HFET) structures, respectively, as well as InP based InAlAs/InGaAs quantum well structures with doped InGaAs two-dimensional electron gas (2DEG) channel are analysed. From the experiments it is found that mobility fluctuation is the only origin for the 1/f noise observed both in InGaAs bulk material and in 2DEG heterostructures of high quality. A Hooge parameter attributed to phonon scattering α_Hphon in the bulk material is found to be about 7×10⁻⁶ and agrees with those obtained from HFET structures with the highest mobilities (α_H≈1.5×10⁻⁵). Furthermore, the Hooge parameter of 2DEG structures strongly depends on the channel design and on the doping concentration in the n-type doped 2DEG channels.     

Dependence of structural and optical properties of QD arrays in an InAs/GaAs system on surface temperature and growth rate

Properties of InAs QD arrays on a <100> GaAs surface in relation to the surface temperature and InAs growth rate are studied experimentally and theoretically. A kinetic model of QD formation in heteroepitaxial growth is developed, which allows the calculation of the mean lateral size and surface density of islands as functions of the growth conditions and duration. Experimental study of optical and structural properties is performed for QDs with an effective thickness of 2 ML, grown at different substrate temperatures and growth rates. The calculated results correlate well with the experimental data. The raising of the surface temperature and slowing of the growth rate result in a considerable increase in the QD mean lateral size and a decrease in their surface density.     

Improvement in the quantum sensitivity of InAs/InAsSb/InAsSbP heterostructure photodiodes

InAs/InAs_0.88Sb_0.12/InAs_0.50Sb_0.20P_0.30 heterostructure photodiodes operating at room temperature in the spectral range 1–4.8 μm are developed. It is shown that the formation of a curvilinear reflecting surface constituted by a number of hemispheres on the rearside of the photodiode chip leads to an increase in the quantum sensitivity of the photodiodes by a factor of 1.5–1.7 at wavelengths in the range 2.2–4.8 μm. At an exposed photodiode area of 0.9 mm² and a p-n junction area of 0.15 mm², a zero-bias differential resistance of 30 Ω and a quantum sensitivity of 0.24 electron/photon at a wavelength of 3 μm are obtained. The operation of a photodiode with re-reflection of the photon flux in the crystal due to reflection from the curvilinear surface of the rearside of the photodiode chip is theoretically analyzed. The possibility of effective conversion of the re-reflected flux of photons into a photocurrent, with a simultaneous decrease in the p-n junction area, is demonstrated. An increase in the quantum sensitivity in the short-wavelength spectral range 1–2.2 μm by 35% relative to the calculated data is observed, which is probably due to impact ionization in the narrow-gap active region.     

New continuous heterostructure field-effect-transistor model andunified parameter extraction technique

A continuous model for heterostructure field-effect transistors (HFETs) suitable for circuit simulation and device characterization is proposed. The model is based on the analytical solution of a two-dimensional Poisson equation in the saturation region. The HFET saturation current and saturation voltage have been experimentally determined by differentiating the output characteristics in a unified and unambiguous way. The results are used for the systematic extraction of device and process parameters. The deduced values agree well with other independent measurements. The results of experimental studies of HFETs with nominal gate lengths of 1, 1.4, 2, and 5 μm are reported. The models and techniques presented here are successfully applied to all these devices. A large short-channel effect is observed for the 1-μm-gate HFET. The gate length dependences of the device parameters determined by the method reveal that the effective gate length in the self-aligned structures is approximately 0.25 μm shorter than the nominal gate length     

Ultra-low temperature OMVPE of InAs and InAsBi

InAs and InAsBi have been grown by atmospheric pressure organometallic vapor phase epitaxy (OMVPE) over a broad temperature range from 600 to as low as 275° C. This is the lowest growth temperature ever reported for conventional OMVPE. It is demonstrated that lowering the growth temperature is the most effective approach for increasing the maximum Bi content in InAsBi alloys where the Bi solubility limit is 0.025 at.%. For example, InAsBi samples with Bi concentrations as high as 6.1 at.% have been successfully grown at a temperature of 275° C. Trimethylindium, arsine, and trimethylbismuth were used as precursors for most experiments. The growth efficiency is a constant for temperatures above 400° C, indicating that the growth rate is diffusion limited. For lower temperatures, it decreases exponentially with decreasing temperature with an activation energy of 24 kcal/mol. Incomplete pyrolysis of TMIn limits the growth rate in this temperature regime. By substituting ethyldimethylindium for TMIn the growth rate can be increased at lower temperatures. Hall effect measurements show that then-type background concentration increases from approximately 2.3 × 10¹⁶ to 10¹⁹ cm⁻³ as the growth temperature decreases from 600 to 325° C. Secondary ion mass spectroscopy results show that the dominant impurity is carbon. Thus, carbon is mainly a donor in these materials. The integrated photoluminescence intensity drops rapidly with decreasing growth temperature.     

Oscillatory characteristic temperature of InAs quantum-dot laser

An InAs quantum-dot laser showed continuous-wave lasing up to 323 K. A high T₀ of over 1000 K was measured below 130 K. The value of T₀ rapidly declined at higher temperatures, and showed an oscillatory behavior above 250 K. The oscillatory changes of T ₀ were accompanied by alternating change in the light output versus current curves above the threshold, suggesting possible participation of higher states in lasing     

Effect of temperature on the electroluminescent properties of mid-IR (λmax ≈ 4.4 μm) flip-chip LEDs based on an InAs/InAsSbP heterostructure

The temperature dependence (20-200°C) of the electrical and electroluminescent properties of a flip-chip light-emitting diode (LED) based on an InAs/InAsSbP heterostructure (λ ≈ 3.37 μm) has been studied. It is shown that the charge transport through the LED is governed by the tunneling-recombination (at a forward bias) and diffusion (at a reverse bias) mechanisms. The peak of the emission spectrum is due to the band-to-band recombination. As the LED is heated, the emission spectrum shifts to longer wavelengths because of the decrease in the energy gap of gallium arsenide. The emission power superexponentially decreases with increasing temperature, which is mainly due to a rise in the Auger recombination rate.     

Resonant-tunnelling hot-electron transistor (RHET) using a GaInAs/(AlGa)InAs heterostructure

A common-emitter current gain of 10 has been measured at 77 K for a 100 nm-base resonant-tunnelling hot-electron transistor (RHET) using a GaInAs/(AlGa)InAs heterostructure. The current gain for 25 nm-base RHETs has reached 25, which is the highest value yet reported for hot-electron transistors, and the collector current peak-to-valley ratio has reached 15.0 for the same device.     

Dependence of Internal Crystal Structures of InAs Nanowires on Electrical Characteristics of Field Effect Transistors

We report on the dependence of internal crystal structures on the electrical properties of a catalyst-free and undoped InAs nanowire (NW) formed on a Si(111) substrate by metal–organic chemical vapor deposition. Cross-sectional transmission electron microscopy images, obtained from four different positions of a single InAs NW, indicated that the wurtzite (WZ) structure with stacking faults was observed mostly in the bottom region of the NW. Vertically along the InAs NW, the amount of stacking faults decreased and a zinc-blende (ZB) structure was observed. At the top of the NW, the ZB structure was prominently observed. The resistance and resistivity of the top region of the undoped InAs NW with the ZB structure were measured to be 121.5 kΩ and 0.19 Ω cm, respectively, which are smaller than those of the bottom region with the WZ structure, i.e., 251.8 kΩ and 0.39 Ω cm, respectively. The reduction in the resistance of the top region of the NW is attributed to the improvement in the crystal quality and the change in the ZB crystal structure. For a field effect transistor with an undoped InAs NW channel, the drain current versus drain–source voltage characteristic curves under various negative gate–source voltages were successfully observed at room temperature.     

High temperature InAs infrared detector based onmetal-insulator-semiconductor structure

The Au/Cr/a-SiN_x:H/(n)InAs/GaAs metal-insulator-semiconductor (MIS) capacitor was fabricated as a basic element of charge injection devices using plasma enhanced chemical vapour deposition. The electrical properties of the capacitor were analysed as a function of temperature using high frequency (1 MHz) capacitance-voltage measurements. It was demonstrated that the capacitor can still be biased into deep depletion at 180 K. When this capacitor is used as an integrated infrared detector in a charge injection device, it exhibits the capacity to detect infrared signals at a temperature of 180 K, higher than that of an InSb infrared detector (77 K), and the device can be cooled thermoelectrically     

Room temperature characterization of Hg1-xCdxTe P-on-n heterostructure photodiodes

Measurements of 77K R_oA and 300K reverse bias dynamic impedance (R_dA) products at one volt reverse bias has been carried out to assess the degree of correlation of this figure of merit. Planar P-on-n heterostructures were grown on near lattice-matched CdZnTe substrates with Hg_1-xCd_xTe (0.20< x <0.30) by molecular beam epitaxy. These devices were passivated with CdTe and doped with indium and arsenic as n- and p-type dopants, respectively. Current-voltage characteristic of these devices exhibit thermally generated dark currents at small and modest reverse bias. We have observed that R_oA values of these long wavelength infrared P-on-n heterostructure photodiodes at 77K correlate with room temperature R_dA values. Diode arrays with high room temperature R_dA values at one volt reverse bias also have high R_oA values at 77K. Similarly, low R_dA values at room temperature indicate poor performance at 77K where deviation from diffusion current occurs at reverse bias of 0.2 to 1 volt at room temperature. The results presented here, for a small samples of devices, demonstrate that room temperature measurements of current-voltage characteristics to evaluate Hg_1-xCd_xTe (0.22< x <0.28) diode performance and array uniformity at lower temperatures can be used. This provides an acceptable criteria for further study at lower temperatures.     

Structural stability of low temperature grown InGaAs/GaAs heterostructure

InGaAs/GaAs superlattice was grown by molecular beam epitaxy (MBE) on GaAs (100) substrate at low substrate temperature (250°C). The as-grown superlattice sample was then annealed at various temperatures for 10 min. The as-grown superlattice was pseudomorphic and stable up to 800°C annealing. Annealing at 850°C or higher temperatures, however, caused strain relaxation accompanying with dislocation generation at the As precipitate. Dislocation generation at the As precipitate was influenced by two factors. The one is lattice mismatch between GaAs and As precipitate, and the other is elastic interaction force acting on the As precipitate.     

A theory of the Hooge parameters of solid-state devices

Handel's theory of quantum 1/f noise is applied to the Hooge parameters of bipolar transistors and various types of FET's. Very low values for the Hooge parameters αHnand αHpfor electrons and holes are obtained. For several cases the experimental data seem to agree with the predicted theoretical limit whereas in other cases the mobility 1/f noise is masked by other noise sources. In good GaAs devices the predicted quantum limit for αHnis reached within a factor 5-10. The theory is also applied to the Hg1-xCdxTe materials and devices. Because of the very low effective masses involved, the theory predicts values as high as 2 × 10^-4-2 × 10^-5, depending onx. What remains presently unexplained are the high values of αHfor semiconductor resistors and long p-n diodes.