Hydrogen passivation in n- and p-type 6H-SiC

Hydrogen passivation effects are found to be much more prevalent in p-type 6H-SiC relative to n-type material. Reactivation of passivated B acceptors occurs at ~700°C, corresponding to a reactivation energy of ~3.3 eV. This is much higher than for passivated acceptors in Si, where reactivation occurs at ≤200°C. The incorporation depth of ²H from a plasma at 200°C is ≤0.1 μm in 30 min, corresponding to a diffusivity approximately two orders of magnitude lower than in Si at the same temperature. The average energy of ions in the ²H plasma has an influence on the peak concentration of incorporated deuterium and on its diffusion depth.     

Electrical band-gap narrowing in n- and p-type heavily doped silicon at 300 K

Based on previous results band-gap narrowing in heavily doped silicon at 300 K is investigated and expressed in terms of impurity size-and-doping effects. The results obtained for n- and p-type heavily doped silicon are compared with other theories and experiments.     

Comparison of current-voltage characteristics of n- and p-type 6H-SiC Schottky diodes

Current-voltage (I–V) characteristics of n- and p-type 6H−SiC Schottky diodes are compared in a temperature range of room temperature to 400°C. While the room temperature I–V characteristics of the n-type Schottky diode after turn-on is more or less linear up to ∼100 A/cm², the I–V characteristics of the p-type Schottky diode shows a non-linear behavior even after turn-on, indicating a variation in the on-state resistance with increase in forward current. For the first time it is shown that at high current densities (>125 A/cm²) the forward voltage drop across p-type Schottky diodes is lower than that across n-type Schottky diodes on 6H−SiC. High temperature measurements indicate that while the on-state resistance of n-type Schottky diodes increases with increase in temperature, the on-state resistance of p-type Schottky diodes decreases with increase in temperature up to ∼330 K.     

Majority-carrier traps in n- and p-type epitaxial GaAs

Majority-carrier traps are characterised for n- and p-type GaAs. Bulk and vapour-phase-epitaxial n GaAs show the same electron-trap centre (0.83 eV). No electron traps were detected in liquid-phase epitaxial n GaAs, but three hole trap centres (0.64, 0.44 and ~ 0.6 eV) were found in p GaAs. The capture cross-section and density of these centres have also been determined.     

Comparison of MOS capacitors on n- and p-type GaN

The electrical characteristics of both n- and p-type GaN metal-oxide semiconductor (MOS) capacitors utilizing plasma-enhanced CVD-SiO₂ as the gate dielectric were measured. Both capacitance and conductance techniques were used to obtain the MOS properties (such as interface state density). Devices annealed at 1000°C/30 min. in N₂ yielded an interface state density of 3.8×10¹⁰ cm⁻² eV⁻¹ at 0.19 eV from the conduction band edge, and it decreased to 1.1×10¹⁰ cm⁻² eV⁻¹ deeper into the band gap. A total fixed oxide charge density of 8×10¹² q cm⁻² near the valence band was estimated. Unlike the symmetric interface state density distribution in Si, an asymmetric interface state density distribution with lower density near the conduction band and higher density near the valence band was determined.     

Growth and characteristics of p-type doped GaAs nanowire

The growth of p-type GaAs nanowires (NWs) on GaAs (111) B substrates by metal-organic chemical vapor deposition (MOCVD) has been systematically investigated as a function of diethyl zinc (DEZn) flow.The growth rate of GaAs NWs was slightly improved by Zn-doping and kink is observed under high DEZn flow.In addition,the I-V curves of GaAs NWs has been measured and the p-type dope concentration under the Ⅱ/Ⅲ ratio of 0.013 and 0.038 approximated to 1019-1020 cm-3.     

Voltage drop in n- and p-type Bragg reflectors for vertical-cavitysurface-emitting lasers

An analysis of carrier transport in n- and p-type distributed Bragg reflectors (DBR) of vertical-cavity surface-emitting lasers that consist of stacks of quarter-wave GaAs-AlAs layers is presented. The analysis is based on the diffusion-drift approximation with the thermionic boundary conditions at heterojunction interfaces. The spatial distribution of carrier effective masses and mobilities has been taken into account. While the voltage drop in n-type DBR is determined mostly by thermionic emission at the interfaces, the drift-diffusion component of the voltage drop is comparable with the thermionic emission in p-type DBR. We present the calculated resistance as a function of graded-region thicknesses and doping levels, which can be useful for low-resistive DBR design     

原位As掺杂p型碲镉汞薄膜的制备研究

非本征p 型掺杂碲镉汞材料可以有效克服少子寿命偏低等问题,提高长波和甚长波红外焦平面器件的性能。本文重点阐述了As 掺杂实现p型掺杂的基础性原理,以及其制备方法,为p-on-n碲镉汞材料器件研究提供依据。     

Heavily p-type doped ZnSe using Te and N codoping

We have studied photoluminescence (PL) of ZnSe samples codoped with Te and N in δ-layers. We have concluded that Te clusters are involved in the PL. We also compared the PL data of samples with lower Te concentrations to those with higher Te concentrations; the results corroborate the Te-cluster conclusion.     

GaN n- and p-type Schottky diodes: Effect of dry etch damage

The reverse breakdown voltage (V_B) and forward turn-on voltage (V_F) of n- and p-GaN Schottky diodes were used to examine the effects of Cl₂/Ar and Ar plasma damage. Even short plasma exposures (4 secs) produced large changes in both V_B and V_F, with ion mass being a critical factor in determining the magnitude of the changes. The damage depth was established to be 500-600 Å and the damaged material could be removed in boiling NaOH solutions, producing a full recovery of the diode properties. Annealing at 700 to 800°C under N₂ produced only a partial recovery of V_B and V_F     

基于GaN材料p型掺杂的研究进展

GaN材料作为第三代半导体材料已成为短波长光电子器件及高频,高压、高温微电子器件制备的最优选材料,而难以获得高质量的P型GaN成为阻碍GaN器件进一步发展和应用的重要原因.介绍了P型掺杂存在的问题,讨论了P型掺杂的激活方法和机理,综述了目前P型掺杂国内外的研究进展情况,最后指出了今后的研究方向.     

Electronic transport in n- and p-type modulation-doped GaInNAs/GaAs quantum wells

We present electronic transport in n- and p-type modulation-doped GaInNAs/GaAs quantum well structures. The Hall mobility of electrons in the n-type material decreases dramatically with increasing nitrogen composition. The mobility of 2D holes in p-modulation-doped quantum wells is significantly higher than that of 2D electrons in n-modulation-doped material with similar nitrogen concentration. The mobility of 2D electrons is discussed using a S-matrix model for N-related alloy scattering. The results indicate that the electron mobility is intrinsically limited by scattering from nitrogen complexes. The high mobility of 2D holes is explained in terms of negligible effect of nitrogen on valance band and the absence of scattering with localized nitrogen complexes.     

Characterization of Hg0.7Cd0.3Te n- on p-type structures obtained by reactive ion etching induced p- to n conversion

This paper presents transport measurements on both vacancy doped and gold doped Hg_0.7Cd_0.3Te p-type epilayers grown by liquid phase epitaxy (LPE), with N_A=2×10¹⁶ cm⁻³, in which a thin 2 μm surface layer has been converted to n-type by a short reactive ion etching (RIE) process. Hall and resistivity measurements were performed on the n-on-p structures in van der Pauw configuration for the temperature range from 30 K to 400 K and magnetic field range up to 12 T. The experimental Hall coefficient and resistivity data has been analyzed using the quantitative mobility spectrum analysis procedure to extract the transport properties of each individual carrier contributing to the total conduction process. In both samples three distinct carrier species have been identified. For 77 K, the individual carrier species exhibited the following properties for the vacancy and Au-doped samples, respectively, holes associated with the unconverted p-type epilayer with p ≈ 2 × 10¹⁶ cm⁻³, μ ≈ 350 cm²V⁻¹s⁻¹, and p ≈ 6 × 10¹⁵ cm⁻³, μ ≈ 400 cm²V⁻¹s⁻¹; bulk electrons associated with the RIE converted region with n ≈ 3 × 10¹⁵cm⁻³, μ ≈ 4 × 10⁴ cm²V⁻¹s⁻¹, and n ≈ 1.5 × 10¹⁵ cm⁻³, μ ≈ 6 × 10⁴ cm²V⁻¹s⁻¹; and surface electrons (2D concentration) n ≈ 9 × 10¹² cm⁻² and n ≈ 1 × 10¹³ cm⁻², with mobility in the range 1.5 × 10³ cm²V⁻¹s⁻¹ to 1.5 × 10⁴ cm²V⁻¹s⁻¹ in both samples. The high mobility of bulk electrons in the RIE converted n-layer indicates that a diffusion process rather than damage induced conversion is responsible for the p-to-n conversion deep in the bulk. On the other hand, these results indicate that the surface electron mobility is affected by RIE induced damage in a very thin layer at the HgCdTe surface.     

Effective recombination levels in n- and p-type silicon irradiated by 4·5 MeV electrons

The effective recombination levels created at room temperature by 4·5 MeV electron irradiation are deduced from the variations in lifetime vs carrier injection rate, electron fluence, and temperature. This paper aims to compare the properties of the created recombination energy levels and defect centers in N- and P-type silicon single crystals. The characteristics of the samples used extend over a wide range of resistivities, doping impurities and crystal growth techniques. A pulsed neodymium laser has been employed to carry out these studies, and the carrier lifetime has been measured by the photoconductivity-decay method. Information on the specific centers is deduced from the comparison of the present macroscopic results on energy levels and annealing studies with the known properties of microscopic defects.From the results obtained, several types of recombination centers are simultaneously created in N- and P-type silicon, and crystal impurities other than oxygen and dopants may play a big part in the constitution of such centers. In the P-type silicon case, 3 types of recombination centers are clearly operative: (1) centers with a ～E_v+0·20 eV energy level, which could be divacancies, and which would cease to act as recombination centers by trapping irradiation induced interstitial carbon atoms, (2) centers with a ～E_v+0·24 eV level which may involve aluminium interstitial atoms, and finally (3) centers with a ～E_v+0·27 eV level, which are K centres. These recombination centers are more or less active, depending on the initial characteristics of the sample. In the N-type silicon case, only two groups of effective recombination levels, ～E_c?0·17 and E_v+0·3 eV, appear in the irradiated materials. However, the effects of centers possibly linked to the presence of contaminants, such as carbon and aluminium, must be added to the known effects of the divacancy, doping atom-vacancy and oxygen-vacancy complexes to explain the carrier lifetime degradation and recovery.     

MOS varactors with n- and p-type gates and their influence on an LC-VCO in digital CMOS

The influence of the gate doping type of the MOS varactor on frequency tuning, phase noise, and frequency sensitivity to supply-voltage variations of a fully integrated inductance-capacitance voltage-controlled oscillator (LC-VCO) is presented. Three varactors in multifinger layout with shallow trench isolation (STI) are compared. The polysilicon gate is either entirely n- or p-doped or the fingers have alternating n and p doping. Differences in capacitance and quality factor are shown. Two identical VCOs with the varactors having n gates or np gates are realized. Homogenous doping increases the VCO tuning range to 1.31 GHz (/spl plusmn/20%) in comparison to 1.06 GHz (/spl plusmn/15%) obtained by mixed doping. However, mixed doping has the advantages of more linear VCO frequency tuning, lower close-in phase noise, and reduced maximum sensitivity to variations in supply voltage. Several varactor parameters are introduced. They allow prediction of the influence of varactors on the performance of a given VCO. With a current consumption of only 1 mA from a supply voltage of 1.5 V, both VCOs show a phase noise of -115 dBc/Hz at 1-MHz offset from a 4-GHz carrier and a VCO figure of merit of -185.3 dBc/Hz.     

Energy-band distortion in highly doped silicon

A plausible model for the doping dependences of the conduction-and valence-band shifts, and of the concomitant narrowings of the optical and electrical energy gaps, caused by high doping concentrations in silicon is developed by refining, extending, and combining previously described theories. A meaningful link is thereby established between the fundamental solid-state physics that underlies the energy-band distortion and the silicon device physics that describes the pragmatic ramifications of it. The important many-body effects, which produce actual rigid shifts in the conduction and valance bands, are identified and characterized, and are shown to exclusively narrow the optical energy gap. The electrical energy-gap narrowing comprises additional effective shifts defined by the band tails due to the randomness of the dopant distribution, which are described. Predictions of the optical and electrical energy-gap narrowings, the difference between which is explained physically for the first time, are shown to agree well with measurements from several independent experiments.     

Morphology and photoluminescence studies of electrochemically etched heavily doped p-type GaAs in HF solution

Porous GaAs layers have been produced by electrochemical anodic etching of (100) heavily doped p-type GaAs substrate in HF solution. Scanning electron microscopy revealed the presence of etch pits ranging in size from 0.01 to 2 μm and they were strongly dependent on the electrochemical etching conditions. The etch pits chemical composition consists of O, Ga and As whereas the porous structure consists predominantly of GaAs as performed by energy dispersive X-ray analyzer. Typical porous structure with pores diameter ranging from 15 to 50 nm has been obtained. Room temperature photoluminescence (PL) investigations reveal the presence of two and in one case three PL bands besides the PL band of the started GaAs. Peaks wavelengths positions were approximately located in 600-900 nm range. The PL bands peaks wavelengths positions depend on the electrochemical etching conditions and they were approximately unchanged with increasing temperature. However, their PL intensity increased slowly with increasing temperature and tend to saturate. The observed PL bands were explained by the quantum confinement effects in GaAs nanocrystallites.     

Transport equations for highly doped devices and heterostructures

An overview of the transport equations describing electron and hole motion and density in solids with nonuniform band structure is presented. This includes materials with graded composition, like heterojunctions, and devices with highly doped regions, like the emitter region of modern bipolar transistors and solar cells. Effects due to carrier degeneracy, changes in the energy band edges, and changes in the density of states produce terms in the carrier- and current-density equations in addition to those found in the conventional Shockley model. These new terms are derived and discussed.The general energy-band diagram relating the electrostatic potential, electron affinity and bandgap is given. The current densities are written in terms of gradients of quasi-Fermi level and the carrier densities in terms of normalization integrals. The concepts of generalized drift and diffusion are discussed. Connections to the work by Van Overstraeten et al. and to Lundstrom et al. are given. The transport equations in the nondegenerate limit are presented. The special case of minority-carrier flow in quasi-neutral material is given. Key approximations used in device analysis are discussed.     

Carrier recombination and lifetime in highly doped silicon

The predominance of phonon-assisted band-band Auger recombination in highly doped silicon is demonstrated by showing that no recombination mechanism involving common (unavoidable) defects in silicon can yield carrier lifetimes that are consistent with the measured lifetimes, which exhibit an inverse-quadratic doping-density dependence, and/or with their temperature dependence. Both trap-assisted-Auger and Shockley-Read-Hall recombination mechanisms are considered, and dependences of the defect density on the doping density, which are implied by theory and experiment, are accounted for.