Minority Hole Mobility Research Articles

Electron beam probing of non-equilibrium carrier dynamics in 18 MeV alpha particle- and 10 MeV proton-irradiated Si-doped β -Ga2O3 Schottky rectifiers

Minority hole diffusion length and lifetime were measured in independent experiments by electron beam-induced current and time-resolved cathodoluminescence in Si-doped β-Ga2O3 Schottky rectifiers irradiated with 18 MeV alpha particles and 10 MeV protons. Both diffusion length and lifetime exhibited a decrease with increasing temperature. The non-equilibrium minority hole mobility was calculated from the independently measured diffusion length and lifetime, indicating that the so-called hole self-trapping is most likely irrelevant in the 77–295 K temperature range.

Vertical carrier transport in strain-balanced InAs/InAsSb type-II superlattice material

Anisotropic carrier transport properties of unintentionally doped InAs/InAs0.65Sb0.35 type-II strain-balanced superlattice material are evaluated using temperature- and field-dependent magnetotransport measurements performed in the vertical direction on a substrate-removed metal-semiconductor-metal device structure. To best isolate the measured transport to the superlattice, device fabrication entails flip-chip bonding and backside device processing to remove the substrate material and deposit contact metal directly to the bottom of an etched mesa. High-resolution mobility spectrum analysis is used to calculate the conductance contribution and corrected mixed vertical-lateral mobility of the two carrier species present. Combining the latter with lateral mobility results from in-plane magnetotransport measurements on identical superlattice material allows for the calculation of the true vertical majority electron and minority hole mobilities; amplitudes of 4.7 ×103 cm2/V s and 1.60 cm2/V s are determined at 77 K, respectively. The temperature-dependent results show that vertical hole mobility rapidly decreases with decreasing temperature due to trap-induced localization and then hopping transport, whereas vertical electron mobility appears phonon scattering-limited at high temperature, giving way to interface roughness scattering at low temperatures, analogous to the lateral electron mobility but with a lower overall magnitude.

Carrier mobility reduction and model in n-type compensated silicon

Research on electrical properties of the compensated silicon is very crucial for understanding the doping layer and compensated substrates of solar cells. Regarding the fact that there are still inadequate experimental data of carrier mobility on the n-type compensated silicon, hence in this paper, both majority electron and minority hole mobilities measured on the n-type compensated solar-grade silicon substrates are presented. Prediction models of carrier mobility are essential for material characterization and device (e.g. solar cells) simulation. However, as prediction models of carrier mobility are commonly established based on the uncompensated silicon, large deviations of carrier mobility have been observed on the compensated silicon. In this work, the standard Klaassen’s model and optimized model for the compensated silicon by Schindler et al. are reviewed and compared to measured carrier mobilities. Moreover, the factors that lead to deviations of Klaassen’s model on the n-type compensated silicon are critically discussed, and then we propose an optimized model for prediction of carrier mobility in the compensated silicon. This model can also be extended to both majority and minority carrier mobilities in p- and n-type compensated silicon and fits well with previous published data as well as carrier mobility data presented here. In addition, evolutions of majority electron and minority hole mobilities as crystal grows are also simulated for n-type compensated Czochralski silicon which agrees well with our measured results.

Nonequilibrium Carrier Diffusion and Recombination in Heavily-Doped and Semi-Insulating Bulk HTCVD Grown 4H-SiC Crystals

We applied four-wave mixing (FWM) technique for investigation of high temperaturechemical vapour deposition (HTCVD) grown 4H-SiC samples with different doping levels. The determined minority electron and hole mobilities in heavily doped crystals at doping densities of 1019 cm-3 were found to be equal to 116 and 52 cm2/Vs. In semi-insulating (SI) crystals, the ambipolar diffusion coefficient Da = 2.6 − 3.3 cm2/s and carrier lifetimes of 1.5 – 2.5 ns have been measured. Irradiation of SI crystals by 6 MeV electrons resulted in essential decrease of carrier lifetime down to ~ 100 ps and clearly revealed the defect-assisted carrier generation with respect to two-photon interband transitions before irradiation.

Majority and minority electron and hole mobilities in heavily doped gallium aluminum arsenide

The majority electron and minority hole mobilities were calculated in Ga1−yAlyAs for donor densities between 1016 and 1019 cm−3. Similarly, the majority hole and minority electron mobilities were calculated for acceptor densities between 1016 and 1020 cm−3. The mole fraction of AlAs, y, varies between 0.0 and 0.3 in these calculations. All the important scattering mechanisms have been included. The ionized impurity and carrier–carrier scattering processes were treated with a quantum-mechanical, phase-shift analysis. These calculations are the first to use a phase-shift analysis for minority carriers scattering from majority carriers in ternary compounds such as Ga1−yAlyAs. The results are in good agreement with experiment for majority mobilities and predict that at high dopant densities minority mobilities should increase with increasing dopant density for a short range of densities. This effect occurs because of the reduction of plasmon scattering and the removal of carriers from carrier–carrier scattering due to the Pauli exclusion principle. These calculations do not treat the density-of-state modifications due to heavy doping, which should have only a small effect on the mobility at room temperature. The results are important for device modeling because of the need to have physically reasonable values for minority mobilities when simulating the electrical behavior of heterojunction bipolar transistors.

Temperature dependence of minority hole mobility in n+-GaAs measured with a new variable temperature technique

The temperature-dependent mobility provides essential information for device design and serves as a sensitive probe of minority carrier scattering physics. As examples, dominant scattering mechanisms are identified by characteristic temperature dependencies of mobility and for low temperature bipolar device optimization, accurate minority carrier mobility data are required. We report the first temperature (T) dependent measurement of minority hole mobility in n+-GaAs. The minority carrier mobility (μ) was measured with the zero-field time-of-flight technique. In this technique, minority carrier diffusivity (D), where De = μkT, is determined from the transient response of a specially designed photodiode that is excited by a high-speed laser. We have extended the technique to permit continuously variable, T-dependent minority mobility measurements. The unique cryostat design, including device mounting, low-loss feedthroughs and temperature measurement scheme, is presented.

A unified model of a poly-Si emitter transistor for various emitter structures

A new unified device model of a polysilicon emitter transistor (PET) is proposed for various emitter structures. More factors influencing the base current are considered in this model and the general expressions for the common emitter current gain (hFE) and the emitter Gummel number (Ge) are derived in an analytical form. From these general expressions we can classify five different PET device structures of PET by specifying some structure parameters of the devices. Ning's theoretical equation for the current gain enhancement factor K and De Graaff's theoretical equation for Ge can be deduced directly from this model. This model is in good agreement with experimental results. The value for the minority hole mobility in polysilicon is also deduced to be in the range of 4.5-6.1 cm2 V-1 s-1 from fitting to the experimental data.

Minority hole mobility in n+GaAs

The minority hole diffusivity, or equivalently the hole mobility, was measured in n+GaAs with the zero-field time-of-flight technique. The minority hole mobility was measured for the donor doping range of 1.3×1017 cm−3 to 1.8×1018 cm−3 and was found to vary from 235 to 295 cm2/V s. At the lower doping level, the minority hole mobility is comparable to the corresponding majority hole mobility, but at 1.8×1018 cm−3 the minority hole mobility was 30% higher than the majority carrier hole mobility. These results have important implications for the design of devices such as solar cells and pnp-heterojunction bipolar transistors.

A two-dimensional ensemble Monte Carlo simulation of hole transport in heavily doped small n-type emitters

An ensemble Monte Carlo simulation of hole transport in the emitters of ultrasmall npn bipolar transistors is presented in this paper. A small number of holes in a heavily doped emitter permit us to follow the entire history of all holes in the emitter over a long period of time. Most of the important scattering mechanisms and the band-to-band Auger recombination are included in the simulator. The minority-hole mobility was calculated and compared with the best existing measurement results. Reasonable agreement between the theory and experiments has been achieved. The fluctuation in the base current, which is a fundamental limitation in scaling bipolar transistors operating at very high speed, was extensively studied.

Effects of using minority hole mobility in n+ emitter on bipolar device modeling

Effects of using minority hole mobility in n+ emitter on bipolar device modeling

Transistor-based studies of heavy doping effects in n-GaAs

The n2ieDp product (where n2ie is the np product and Dp is the minority hole mobility) in heavily doped n-GaAs has been measured by electrical characterization of p-n-p GaAs homojunction transistors with base dopings ranging from approximately 1×1017 to 9×1018 cm−3. The measured n2ieDp product decreases as the doping density increases. These results suggest that nie is roughly constant with doping density, in sharp contrast to the large increase observed for p-type GaAs. This work shows that when designing GaAs bipolar devices, it is important to consider the large difference in effective band gap between n+ and p+ regions.

Monte Carlo studies on hole mobility in heavily doped n-type silicon

The minority hole mobility in heavily doped n-type silicon is calculated by means of the Monte Carlo technique from 77K to 350K. Hole-electron scattering and hole-plasmon scattering are included in the simulation. The calculated mobility, based on the Born approximation with the third-body exclusion, is close to the recently measured mobility. The temperature dependence of the calculated mobility is in approximate agreement with the measurements.

Majority and minority electron and hole mobilities in heavily doped GaAs

The majority electron and minority hole mobilities have been calculated in GaAs for donor densities between 5×1016 and 1×1019 cm−3. Similarly, the majority hole and minority electron mobilities have been calculated for acceptor densities between 5×1016 and 1×1020 cm−3. All the important scattering mechanisms have been included. The ionized impurity and carrier–carrier scattering processes have been treated with a phase-shift analysis. These calculations are the first to use a phase-shift analysis for minority carriers scattering from majority carriers. The results are in good agreement with experiment, but predict that at high dopant densities minority mobilities should increase with increasing dopant density for a short range of densities. This effect occurs because of the reduction of plasmon scattering and the removal of carriers from carrier–carrier scattering because of the Pauli exclusion principle. Some recent experiments support this finding. These calculations do not treat the density-of-states modifications due to heavy doping, which should have only a small effect on the mobility at room temperature. The results are important for device modeling because of the need to have values for minority mobilities.

Minority-carrier transport parameters in degenerate n-type silicon

Direct measurements of the minority-hole transport parameters in degenerate n-type silicon were done by analyzing transient photocurrent in the frequency domain. Minority-hole mobility is found to increase with doping for dopings larger than 4*10/sup 19/ cm/sup -3/. The ratio of minority-hole to majority-hole mobility is found to be about 2.8 at N/sub D/=7.2*10/sup 19/ cm/sup -3/. The measured lifetime shows a strongly Auger-dependent mechanism. The extracted Auger coefficient at 296 K is C/sub n/=2.22*10/sup -31/ cm/sup 6/-s/sup -1/, and is in agreement with that reported on other works. Self-consistent checking is used to validate the accuracy of the measured results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Temperature dependence of minority hole mobility in heavily doped silicon

Temperature dependence of the minority hole mobility μp(ND,T) in heavily doped n+ silicon in the doping range from 1018 to 2.4×1019 cm−3 was investigated. The preliminary measurements show that the mobility is strongly temperature dependent. For temperatures below 200 K the minority-carrier hole mobility increases with increasing doping, in contrast to the opposite dependence for the majority hole mobility in p+ silicon. Analytical fits to the measured data useful for low-temperature modeling for bipolar devices are given.

Modeling of currents in a vertical p-n-p transistor with extremely shallow emitter

Detailed simulations of the collector current in a vertical poly-emitter p-n-p transistor have been carried out to verify the minority-hole mobility model of S.E. Swirhun et al. (ibid., vol.7, no.3, p.168-71, 1986). The simulations were based on the SIMS profile, incorporating all published physical parameters, and the results showed good agreement with the measurements for base doping ranging from 10/sup 18/ to 10/sup 19/ cm/sup -3/. In addition, the effective surface recombination velocity of electrons at the p/sup +/ poly/Si interface was found by fitting the measured base current to be approximately 1.4*10/sup 5/ cm/s, which is comparable to its n-p-n counterpart. >

Long minority hole diffusion length and evidence for bulk radiative recombination limited lifetime in InP/InGaAs/InP double heterostructures

Minority hole diffusion length, lifetime, and mobility for undoped InGaAs were measured at 297 and 77 K in metalorganic chemical vapor deposited InP/InGaAs/InP double heterostructures using continuous-wave and pulsed optical beam induced current techniques. A hole diffusion length Lp=140 μm, a lifetime τp=18.5 μs, and a mobility μp=425 cm2/(V s) were obtained at room temperature. To the best of our knowledge, these properties are the highest reported values for InGaAs. The measured carrier lifetime and its temperature dependence are consistent with bulk radiative recombination in undoped InGaAs.

VIB-7 implications of the temperature dependences of minority-hole mobility and bandgap narrowing in n+emitters

VIB-7 implications of the temperature dependences of minority-hole mobility and bandgap narrowing in n⁺emitters

An empirical fit to minority hole mobilities

Minority hole mobilities in highly-doped n-type silicon are determined by electron-beam-induced current measurements. They are used in conjunction with existing data taken from the literature to derive an empirical expression for the minority hole moblility as a function of majority-carrier density 1014cm-3≤ N D ≤ cm-3. It is anticipated that this empirical fit will be valuable in device modeling.

Hole and electron mobilities in heavily doped silicon: comparison of theory and experiment

Most device models for npn or pnp transistors assume that hole (electron) mobilities in n-type and p-type silicon are equal. Partial-wave phase shift calculations for the contributions of carrier-dopant ion scattering to the carrier mobilities lead to unequal minority hole (electron) and majority hole (electron) mobilities at the same doping density. These calculations are valid over the doping range of 2 x 10 19 to 8 x 10 19 cm −3 in n-type and p-type silicon and contain the assumptions that the holes and electrons move in isotropic parabolic energy bands and are scattered by the screened Coulomb potentials of the dopant ions. When the effects of carrier-acoustic phonon and carrier-carrier scatterings are included, these calculations agree to within the spread of experimental value for the majority mobilities reported in the literature. This agreement is a substantial improvement by factors of 2–4 over the results of earlier theories such as first order Born and nondegenerate theories. The results of this work, particularly the inequality of minority and majority carrier mobilities, have implications for the modeling of both bipolar and field effect transistors.