Voltage dependence of the differential capacitance of a p +-n junction

The dependences of the differential capacitance and current of a p ⁺-n junction with a uniformly doped n region on the voltage in the junction region are calculated. The p ⁺-n junction capacitance controls the charge change in the junction region taking into account a change in the electric field of the quasi-neutral n region and a change in its bipolar drift mobility with increasing excess charge-carrier concentration. It is shown that the change in the sign of the p ⁺-n junction capacitance with increasing injection level is caused by a decrease in the bipolar drift mobility as the electron-hole pair concentration in the n region increases. It is shown that the p ⁺-n junction capacitance decreases with increasing reverse voltage and tends to a constant positive value.     

Photoelectric properties of p +-n junctions based on 4H-SiC ion-implanted with aluminum

The photoelectric properties of p ⁺-n junctions that were based on 4H-SiC ion-implanted with aluminum and were formed in lightly doped n-type epitaxial layers grown by chemical vapor deposition were studied. It is shown that such photodetectors combine in full measure the advantages of photostructures formed on the basis of Schottky barriers and epitaxial p-n junctions. The results of the theoretical calculation of spectral characteristics of ion-implanted photodetectors are in good agreement with experimental data. The structures feature an efficiency of collection of nonequilibrium charge carriers close to 100% in the spectral range of the photon energies of 3.5–4.25 eV.     

Measurement of J/V characteristics of a GaAs submicron n+-n?-n+ diode

The J/V characteristics of a GaAs 0.24 ?m channel length n+-n?-n+ diode have been measured at 8 K, 77 K and 300 K. Good agreement is observed with the J/V predictions recently reported by Awano et al. using a Monte-Carlo simulation of a similar device. This verifies the accuracy of their model, and substantiates their findings that electron transport in a 0.25 ?m channel is near-ballistic at 77 K, with a peak ensemble-average electron velocity approaching 108 cm s?1 for an ensemble-average energy just under 0.36 eV. An effective time-average velocity of about half this value can be expected for the total channel transit.     

Spectrometric properties of SiC detectors based on ion-implanted p +-n junctions

Results of spectrometric studies of nuclear radiation detectors based on p ⁺-n junctions formed in 4H-SiC films are presented for the first time. The junctions were fabricated by ion implantation of aluminum into 26-μm-thick CVD-grown epitaxial 4H-SiC layers with an uncompensated donor concentration of (3–5) × 10¹⁵ cm^?3. The detector characteristics were measured in testing with natural-decay alpha particles with energies of 3.35 and 5.4 MeV. The collection efficiency of charge generated by 3.35 MeV alpha particles was as high as 100% at an energy resolution of ? 2%.     

带有P型埋层的新型双栅SOI MOSFET

本文提出一种超低比导通电阻(Ron,sp)可集成的SOI 双栅triple RESURF (reduced surface field)的n型MOSFET (DG T-RESURF)。这种MOSFET具有两个特点：平面栅和拓展槽栅构成的集成双栅结构(DG),以及位于n型漂移区中的P型埋层。首先, DG形成双导电通道并且缩短正向导电路径,降低了比导通电阻。DG结构在反向耐压时起到了纵向场板作用,提高了器件的击穿电压特性。其次, P型埋层形成triple RESURF结构 (T-RESURF),这不仅增加了漂移区的浓度,而且调节了器件的电场。这在降低了比导通电阻的同时提高了击穿电压。最后,与p-body区连接在一起的P埋层和拓展槽栅结构,可以显著降低击穿电压对P型埋层位置的敏感性。通过仿真,DG T-RESURF的击穿电压为325V,比导通电阻为8.6 mΩ?cm2,与平面栅single RESURF MOSFET(PG S-RESURF)相比,DG T-RESURF的比导通电阻下降了63.4%,击穿电压上升9.8%。     

High voltage SOI LDMOS with a compound buried layer

An SOI LDMOS with a compound buried layer (CBL) was proposed. The CBL consists of an upper buried oxide layer (UBOX) with a Si window and two oxide steps, a polysilicon layer and a lower buried oxide layer (LBOX). In the blocking state, the electric field strengths in the UBOX and LBOX are increased from 88 V/μm of the buried oxide (BOX) in a conventional SOI (C-SOI) LDMOS to 163 V/μm and 460 V/μm by the holes located on the top interfaces of the UBOX and LBOX, respectively. Compared with the C-SOI LDMOS, the CBL LDMOS increases the breakdown voltage from 477 to 847 V, and lowers the maximal temperature by 6 K.     

具有补偿埋层的槽型埋氧层SOI高压器件新结构

A new silicon-on-insulator(SOI) high-voltage MOSFET structure with a compensation layer on the trenched buried oxide layer(CL T-LDMOS) is proposed.The high density inverse interface charges at the top surface of the buried oxide layer(BOX) enhance the electric field in the BOX and a uniform surface electric field profile is obtained,which results in the enhancement of the breakdown voltage(BV).The compensation layer can provide additional P-type charges,and the optimal drift region concentration is increased in order to satisfy the reduced surface electric field(RESURF) condition.The numerical simulation results indicate that the vertical electric field in the BOX increases to 6 MV/cm and the B V of the proposed device increases by 300%in comparison to a conventional SOI LDMOS,while maintaining low on-resistance.     

Origin and modeling of the frequency dependent output conductancein microwave GaAs MESFET's with buried p layer

This paper presents the results of measurements and modeling of the frequency dependent output admittance of GaAs microwave MESFET's with and without the buried p layer constructions. The output conductance of devices without the buried p layer shows a transition from a low to a higher value typically within the frequency range of 10 Hz-100 Hz at 300 K, and 10 KHz-100 KHz at 367 K. The shape of this transition is determined by the presence of multiple deep levels at the channel-substrate interface, while the magnitude of the higher value of the output conductance is determined by the transconductance of the substrate-controlled parasitic FET. The addition of a buried p layer beneath the channel region results in a parasitic n-p-n bipolar transistor without completely eliminating the parasitic FET action. Results of our study show that the combined effects of these two parasitic transistors on the output conductance of the buried p layer device becomes relatively independent of frequency above 10 Hz at 300 K. However, at higher temperatures the frequency dispersion of the output conductance becomes significant at frequencies above 10 Hz. At low frequencies the parasitic FET causes a very high output capacitance, whereas the parasitic BJT action causes a high negative output capacitance. For the purpose of modeling of the output admittance, this paper indicates how the parameters of the parasitic FET and BJT can be determined by direct measurements on the MESFET's. The paper also suggests how the parameters of these parasitic transistors can be tailored by possible device structural changes, in order to achieve MESFET's with negligible dispersion of output conductance     

Edge electroluminescence in small-area silicon p +-n diodes heavily doped with boron: Analysis of model representations

The experimental results and model representations of the edge electroluminescence of two published studies for small-area silicon p ⁺-n diodes heavily doped with boron are analyzed. In one of these studies it was assumed that edge electroluminescence appears in the p ⁺ region of the diode, and in the other, in the n region of the diode. In the latter case, it was demonstrated that electroluminescence indeed arose in the n region and was caused predominantly by the radiative recombination of free excitons. It is shown that similar model concepts are also applicable to the other study. Based on several independent experimental studies (of edge photoluminescence, electroluminescence, and radiation absorption by free carriers), it is demonstrated that the linear or close-to-linear dependences of the edge-luminescence intensity on the excitation intensity, observed in single-crystal silicon at high injection levels, are caused by the close-to-linear dependences of the exciton concentration on the free-carrier concentration. The results of this study extend the capability of luminescence methods for determining the carrier lifetimes to the region of high injection levels.     

Silicon-on-insulator structures with a nitrogenated buried SiO<Subscript>2</Subscript> layer: Preparation and properties

Electrical properties of silicon-on-insulator (SOI) structures with buried SiO₂ layer implanted with nitrogen ions are studied in relation to the dose and energy of N⁺ ions. It is shown that implantation of nitrogen ions with doses >3 × 10¹⁵ cm⁻² and an energy of 40 keV brings about a decrease in the fixed positive charge in the oxide and a decrease in the density of surface stares by a factor of 2. An enhancement of the effect can be attained by lowering the energy of nitrogen ions. The obtained results are accounted for by interaction of nitrogen atoms with excess silicon atoms near the Si/SiO₂ interface; by removal of Si-Si bonds, which are traps of positive charges; and by saturation of dangling bonds at the bonding interface of the SOI structure.     

Negative capacitance (impedance of the inductive type) of silicon p +-n junctions irradiated with fast electrons

Silicon p ⁺-n junction diodes irradiated with 3.5-MeV electrons (with the dose of 4 × 10¹⁶ cm^?2) are studied. The diodes’ inductance (L) was measured at a frequency f = 1 MHz with the amplitude of alternating current equal to 0.25 mA. Simultaneously with measurements of L at alternating current, a direct current was passed through the forward-biased diode, which brought about the injection of minority charge carriers into the base. In order to identify both of the mechanisms that give rise to the inductive-type impedance in irradiated diodes with the p ⁺-n junction and the main radiation defects that are directly involved in the formation of this impedance, irradiated samples were annealed isochronously in the temperature range T _a = 225–375°C with sub-sequent study of the main characteristics of the defects by deep-level transient spectroscopy. It is shown that the inductive-type impedance in irradiated diodes is caused by the processes of capture and retention of charge carriers injected into the base at the trapping centers for a time ～1/2f, i.e., for a half-period of oscillations. It is also shown that the trapping centers are the vacancy-oxygen complexes introduced by irradiation with electrons.     

Resistive switching properties of a thin SiO2 layer with CeOx buffer layer on n+ and p+ Si bottom electrodes

Resistive switching properties of a 2-nm-thick SiO₂ with a CeO_x buffer layer on p⁺ and n⁺ Si bottom electrodes were characterized. The distribution of set voltage (V_set) with the p⁺ Si bottom electrode devices reveals a Gaussian distribution centered in 4.5 V, which reflects a stochastic nature of the breakdown of the thin SiO₂. Capacitance–voltage (C–V) measurements indicate the trapping of electrons by positively shifting the C–V curve by 0.2 V during the first switching cycle. On the other hand, devices with the n⁺ Si bottom electrodes showed a broad distribution in V_set with a mean value higher than that of p⁺ Si bottom electrode devices by 0.9 V. Although no charge trapping was observed with n⁺ Si bottom electrode devices, a degradation in interface states was confirmed, causing a tail in the lower side of the V_set distribution. Based on the above measurements, the difference in the V_set can be understood by the work function difference and the contribution of electron trapping.     

复合埋层上的薄层SOI-LDMOS功率器件

为了提高SOI-LDMOS功率器件击穿电压及相关性能,针对薄层SOI-LDMOS功率器件提出了一种新结构,在新结构中引入了复合埋层,它由p埋层与Si3N4绝缘介质埋层构成。复合埋层不仅改善了比导通电阻与耐压的关系,而且还缓解了自热效应。仿真结果表明,在漂移区长度为57 m时,新结构耐压达到了1052 V,与CamSemiSOI相当,而比导通电阻与表面最高温度分别比CamSemi SOI降低了233.05.mm2和64 K。     

Hydrogen passivation of n+p and p+n heteroepitaxial InP solar cell structures

Dislocations and related point defect complexes caused by lattice mismatch currently limit the performance of heteroepitaxial InP cells by introducing shunting paths across the active junction and by the formation of deep traps within the base region. We have previously demonstrated that plasma hydrogenation is an effective and stable means to passivate the electrical activity of such defects within heteroepitaxial InP layers. In this work, we present our first results on the hydrogen passivation of ac tual heteroepitaxial n⁺p and p⁺n InP cell structures grown on GaAs substrates by metal organic chemical vapor deposition (MOCVD). We have found that a 2-h exposure to a 13.56-MHz hydrogen plasma at 275°C reduces the deep level co ncentration in the base regions of both n⁺p and p⁺n heteroepitaxial InP cell structures from as-grown values of 5–7 × 10¹⁴ cm⁻³, down to 3–5 × 10¹² cm⁻³. All dopants were successfully reactivated by a 400°C, 5-min anneal with no detectable activation of deep levels. Current-voltage (I-V) analysis indicated a subsequent ∼100-fold decrease in reverse leakage current at 1 V reverse bias, and an impro ved built-in voltage for the p⁺n structures. In addition to being passivated, dislocations are also shown to participate in secondary interactions during hydrogenation. We find that the presence of dislocations enhances hydrogen diffusion into the cell structure and lowers the apparent dissociation energy of Zn-H complexes from 1.19 eV for homoepitaxial Zn-doped InP to 1.12 eV for heteroepitaxial Zn-doped InP. This is explained by additional hydrogen trapping at dislocations subsequent to the r eactivation of Zn dopants after hydrogenation.     

Hydrogen-induced splitting in silicon over a buried layer heavily doped with boron

Formation of interior hydrogen-passivated surfaces in hydrogen-implanted single-crystal Si containing a buried layer heavily doped with boron is investigated. With the use of the infrared absorption spectroscopy, it is shown that, upon annealing, the composition of hydrogen-containing defects in Si samples containing a buried heavily doped layer is the same as in Si samples that do not have such a layer. However, the presence of a heavily doped layer enhances the blistering and exfoliation of a thin silicon film from the Si sample, and the activation energies of the relevant processes change. Thus, the process of development of cavities in such layers changes upon thermal annealing. The depth at which hydrogen-passivated surfaces are formed corresponds to the projected range of H ions in Si, which also corresponds to the depth at which the B-doped layer is located. When a thin exfoliated film is transferred onto an insulator to form a silicon-on-insulator structure, the surface roughness of the film decreases by a factor of 2–5.     

A formula for the concentration profile of a buried layer with back diffusion

A simple formula allows an accurate dopant concentration profile to be calculated for a Gaussian buried layer with back diffusion into an epitaxial layer. The formula is valid when the drive-in diffusion is dominant, when the back diffusion is dominant, and for intermediate cases.     

Features of the electroluminescence spectra of quantum-confined silicon p +-n heterojunctions in the infrared spectral region

The results of studying the characteristics of optical emission in various regions of quantum-confined silicon p ⁺-n heterojunctions heavily doped with boron are analyzed. The results obtained allow one to conclude that near-infrared electroluminescence arises near the heterointerface between the nanostructured wide-gap silicon p ⁺-barrier heavily doped with boron and n-type silicon (100), the formation of which included the active involvement of boron dipole centers.     

Ultrashallow p +-n junctions in silicon (100): Electron-beam diagnostics of the surface zone

Ultrashallow p ⁺-n junctions formed in silicon (100) under nonequilibrium impurity diffusion conditions are analyzed by electron-beam diagnostics of the surface zone using a probe of low-to medium-energy electrons. The energy dependence of the radiation conductivity is investigated, along with its distribution over the area of the p ⁺-n junction. This procedure can be used to determine the depth distribution (in the crystal) of the probability of separation of electron-hole pairs by the field of the p-n junction; the experimental results show that this distribution differs according to whether the kick-out mechanism or the dissociative vacancy mechanism of impurity diffusion is predominant as the basis of formation of the ultrashallow p ⁺-n junctions. Also reported here for the first time are the results of investigations of the distribution of secondary point centers formed near the boundary of the ultrashallow diffusion profile, which exert a major influence on the transport of nonequilibrium carriers. The data obtained in the study demonstrate the possibility of improving the efficiency of photodetectors, α-particle detectors, and solar batteries constructed on the basis of ultrashallow p-n junctions. Fiz. Tekh. Poluprovodn. 32, 137–144 (February 1998)     

Ultrashallow p +-n junctions in Si(111): Electron-beam diagnostics of the surface region

Ultrashallow p ⁺-n junctions fabricated in Si(111) are investigated by low-and intermediateenergy electron-beam probing of the surface region in order to determine how the crystallographic orientation of the silicon films affects the mechanisms for nonequilibrium diffusion of boron. A comparative study is made of p ⁺-n junctions made on both (111) and (100) silicon with regard to how the irradiation-induced conductivity depends on the energy of the primary electron beam, and also its distribution with area. Using this method, it is possible to determine how the probability of an electron-hole pair being separated by the electric field of the Si(111) and Si(100) p ⁺-n junctions varies with depth into the crystal, which experiments show is different, depending on whether diffusive motion of impurities is dominated by the kick-out or dissociative-vacancy mechanisms. It was found that for boron in silicon the kick-out type of diffusion mechanism is strongly enhanced in the [111] crystallographic direction, whereas diffusion in the [100] direction is primarily driven by vacancy mechanisms. It is shown that collection of nonequilibrium carriers in the p ⁺-n junction field is strongly enhanced when the diffusion profile consists of certain combinations of longitudinal and transverse quantum wells. Fiz. Tekh. Poluprovodn. 33, 58–63 (January 1999)