P-type Barrier Research Articles

SiC superjunction MOSFET with Schottky diode for improving short-circuit and reverse recovery ruggedness

In this article, a novel SiC superjunction MOSFET with Schottky diode containing N- and P-type barrier is proposed to improving short-circuit and reverse recovery ruggedness, investigated by TCAD simulations. The adoption of superjunction and p-shields structure can reduce saturation current, and thus, improve short-circuit capability. A fine gate oxide providing long-term reliability of the device is obtained. Also, N-type Schottky diode for electrons is used to dampen bipolar conduction of the parasitic body diode, while P-type Schottky diode for holes is introduced to constrain the hole inflow and extraction attributed to the transient variation of the superjunction. As a result, compared with an SBD-wall-integrated trench MOSFET (SWITCH-MOS), a low on-resistance and high breakdown voltage of the proposed structure are gained. More importantly, the proposed device exhibits stronger temperature-dependent immunity. As expected, simulation results indicate that the proposed device under 10 nH stray inductance shows a 30%–50 % reduction in the peak reverse recovery current and a 50%–70 % decrease in the current rising slope of reverse recovery, compared to only a single superjunction, when the metal workfunction varies from 5.1 to 5.6 eV. Moreover, the short-circuit withstanding time of the proposed structure increases roughly 2 times longer than that of SWITCH-MOS.

Auger-suppression in barrier-blocking HgCdTe long-wavelength infrared detector

Throughout, both the Auger-suppression effect and barrier-blocking devices have been regarded as highly promising solutions for achieving high- operation-temperature (HOT) in long-wave infrared (LWIR) HgCdTe devices. Herein, two structural designs of pBin-type barrier-blocking LWIR HgCdTe devices were introduced and analyzed, accompanied by an extensive investigation into the Auger-suppression effect within the designed structures. It was observed that this unique structural approach has the potential to enhance the operational temperature of HgCdTe barrier-blocking devices. A strong dependency of the Auger suppression effect on the doping concentration within the absorption region was revealed through the analysis of absorption region structural parameters. Furthermore, the analysis of band structures for different design configurations demonstrated that the structural design involving p-type barrier layers can effectively position the barrier at the conduction band, eliminating the reliance on valence band-offset with respect to barrier layer structural parameters. Consequently, the structural design and fabrication processes of the devices were significantly simplified. These discoveries offer theoretical guidance for the simplification of structural design and fabrication processes in HOT barrier-blocking HgCdTe devices, emphasizing the potential of pBin-type structures in enhancing device performance and achieving elevated operational temperatures.

Low-efficiency-droop c-plane InGaN/GaN light-emitting diodes through the use of thick single quantum wells and doped barriers

Efficiency droop at high current densities is a problem for InGaN-based light-emitting diodes (LEDs), especially for conventional c-plane devices. The large internal electric fields in c-plane quantum wells (QWs) lead to an increase in the active region carrier density (n), causing the electrical efficiency droop onset to occur at low current densities. Here, we present an approach to reduce the internal electric fields (Eint) in c-plane QWs by placing doped p-type and n-type GaN barriers close to the QW. The reduced Eint also allows a thick QW active region design, which helps to lower n to further reduce the droop. The concept of using doped barriers to control Eint is explained using theory and device simulations. Following that, multiple series of thick single QW (SQW) LEDs were grown and characterized. Key parameters in the epitaxial design such as the doping levels and the relative position of the doped barriers were systematically studied and optimized. By using optimized doped barriers and a thick SQW, c-plane LEDs with a low-efficiency droop of 14% at 300 A/cm2 [with respect to the peak external quantum efficiency (EQE)] and a high peak EQE of 49% were demonstrated.

Disclosing the nature of vacancy defects in α-Ag2WO4

Defects at semiconductors with electron acceptor and donor sites govern the electronic and optoelectronic applications due to their unique electronic properties. This work provides deep insight into the nature of defects and the conduction mechanism in α-Ag2WO4. To this aim, a detailed analysis of the results of XRD with Rietveld refinements, FE-SEM images, and measurements of different spectroscopies (impedance, positron annihilation lifetime, and photoluminescence) are carried out on α-Ag2WO4 samples synthesized by a simple co-precipitation method. Two types of vacancy defects: cationic O-vacancies, and anionic Ag or Ag–O vacancy complexes are elucidated with a Schottky p-type potential barrier. The results indicate that the Ag vacancies remain constant during thermal treatment, while an opposite effect is found for the oxygen vacancies. This behavior governs the multifunctional properties of α-Ag2WO4 semiconductors via a tunneling plus thermionic conduction mechanism.

Impact of doped barriers on the recombination coefficients of c-plane InGaN/GaN single quantum well light-emitting diodes

Differential carrier lifetime measurements were performed on c-plane InGaN/GaN single quantum well (QW) light-emitting diodes (LEDs) of different QW indium compositions as well as with and without doped barriers. Mg-doped p-type and Si-doped n-type barriers close to the QW were used to reduce the net internal electric field in the QW, thereby improving the electron–hole wavefunction overlap on the LEDs. LEDs with doped barriers show short lifetimes and low carrier densities in the active region compared to the reference LEDs. The recombination coefficients in the ABC model were estimated based on the carrier lifetime and quantum efficiency measurements. The improvement in the radiative coefficients in the LEDs with doped barriers coupled with the blueshift of the emission wavelengths indeed indicates an enhancement in wavefunction overlap and a reduction of quantum confined Stark effect as a result of the reduced internal electric field. However, doped barriers also introduce non-radiative recombination centers and thereby increase the Shockley–Read–Hall (SRH) coefficient, although the increment is less for LEDs with high indium composition QWs. As a result, at high indium composition (22%), LEDs with doped barriers outperform the reference LEDs even though the trend is reversed for LEDs with lower indium composition (13.5%). Despite the trade-off of higher SRH coefficients, doped barriers are shown to be effective in reducing the internal electric field and increasing the recombination coefficients.

High-performance vertical GaN field-effect transistor with an integrated self-adapted channel diode for reverse conduction

A vertical GaN field-effect transistor with an integrated self-adapted channel diode (CD-FET) is proposed to improve the reverse conduction performance. It features a channel diode (CD) formed between a trench source on the insulator and a P-type barrier layer (PBL), together with a P-shield layer under the trench gate. At forward conduction, the CD is pinched off due to depletion effects caused by both the PBL and the metal–insulator–semiconductor structure from the trench source, without influencing the on-state characteristic of the CD-FET. At reverse conduction, the depletion region narrows and thus the CD turns on to achieve a very low turn-on voltage (V F), preventing the inherent body diode from turning on. Meanwhile, the PBL and P-shield layer can modulate the electric field distribution to improve the off-state breakdown voltage (BV). Moreover, the P-shield not only shields the gate from a high electric field but also transforms part of C GD to C GS so as to significantly reduce the gate charge (Q GD), leading to a low switching loss (E switch). Consequently, the proposed CD-FET achieves a low V F of 1.65 V and a high BV of 1446 V, and V F, Q GD and E switch of the CD-FET are decreased by 49%, 55% and 80%, respectively, compared with those of a conventional metal–oxide–semiconductor field-effect transistor (MOSFET).

An Improved P-Type Doped Barrier Surface AlGaN/GaN High Electron Mobility Transistor with High Power-Added Efficiency.

An improved P-type doped barrier surface AlGaN/GaN high electron mobility transistor with high power-added efficiency (PDBS-HEMT) is proposed in this paper. Through the modelling and simulation of ISE-TCAD and ADS software, the influence of the P-type doped region on the performance parameters is studied, and the power-added efficiency (PAE) obtained and effectively improved is further verified. The drain saturation current and the threshold voltage of PDBS-HEMT has no major change compared with the traditional structure; the peak transconductance decreases slightly, but the breakdown voltage is significantly enhanced. Furthermore, the gate-source capacitance and gate-drain capacitance are reduced by 14.6% and 14.3%, respectively. By simulating the RF output characteristics of the device, the maximum oscillation frequency of the proposed structure is increased from 57 GHz to 63 GHz, and the saturated output power density is 10.9 W/mm, 9.3 W/mm and 6.4 W/mm at the frequency of 600 MHz, 1200 MHz and 2400 MHz, respectively. The highest PAE of 88.4% was obtained at 1200 MHz. The results show that the PDBS structure has an excellent power and efficiency output capability. Through the design of the P-type doped region, the DC and RF parameters and efficiency of the device are balanced, demonstrating the great potential of PDBS structure in high energy efficiency applications.

Understanding the $C-V$ Characteristics of InAsSb-Based nBn Infrared Detectors With N- and P-Type Barrier Layers Through Numerical Modeling

Capacitance–voltage ( C–V ) profiling is a useful technique for accurate and non-destructive determination of carrier concentrations in semiconductor materials. Recently, this measurement has been applied to the infrared barrier detector to determine the doping densities of the absorber and contact layers. This paper provides three contributions to the development of barrier detectors. First, we develop a physics-based semi-analytical model for computing the C–V characteristics derived from metal–oxide–semiconductor and heterojunction device physics and show that it is in agreement with results obtained from drift-diffusion simulations. Second, we assess the possibility of using the developed model to determine not only the absorber and contact doping densities, but also the doping density and thickness of the barrier layer. Lastly, we use the same drift-diffusion methodology to conduct a comprehensive parametric study of the C–V profile for a variety of absorber n-type doping densities, barrier N- and P-type doping densities, barrier thicknesses, and contact layer n-type doping densities. We also offer an extensive discussion of the role of the various device parameters on shaping the C–V profile. While this paper uses the InAsSb and AlAsSb material system, the analysis can be extended to other materials used to implement barrier devices, such as HgCdTe or superlattices.

Effect of slit-type barrier on characteristics of water-dominant debris flows: small-scale physical modeling

Slit-type barriers, one of open-type barriers, are widely used as active measures to mitigate potential risk and damage by debris flows, and those are designed and installed to reduce the flow energy by only passing relatively small debris. However, the mechanisms of slit-type barriers in reducing the debris flow velocity and debris volume remain poorly understood because of the lack of well-controlled and reliable physical modeling results. This study explored the influence of various arrangements of slit-type barriers, including P-type barriers in which each rectangular barrier was placed in parallel and V-type barriers where the barriers were placed in a V-shape, on characteristics of water-dominant debris flows via small-scale model experiments. The debris flow events were reproduced against the slit-type barriers, where the velocity reduction and trap ratio were monitored, varying the angle and shape of barrier arrangements. The velocity reduction and trap ratio appeared to increase as the angle of the barrier wall decreased because of the decreased opening ratio. The V-type barriers resulted in higher velocity reduction and trap ratio than the P-type, primarily because of the smaller effective opening ratio and the more backwater effect. In addition, as the debris contained more boulders, the extent of velocity reduction and debris trap became greater in all barrier types. Two types of opening ratios, the projected and effective opening ratios, were correlated to the interactions between debris and walls. The obtained results provide baseline data for the optimum design of slit-type barriers against debris flow and suggest that the slit-type barriers can effectively manage the risk of damage by debris flows.

Performance enhancement of blue light-emitting diodes by using special designed n and p-type doped barriers

The characteristics of the nitride-based blue light-emitting diode (LED) by using special designed n and p-type doped barriers have been analyzed numerically in this paper. The internal quantum efficiency (IQE), carrier concentrations in the quantum wells (QWs), energy band diagrams, emission spectra and electrostatic fields are investigated. The simulation results indicate that the proposed LED by using the special designed n and p-type doped barriers has a strong enhancement in the optical output power. The improved performance is mainly attributed to the change of electrical field in the active region, resulting in superior electron confinement and improved hole injection efficiency. Further simulation results also indicate that the proposed LED without the p-AlGaN EBL possesses much better hole uniformity, which is due to the reversed electrostatic field in the last barrier.

Mn Related Defect Levels in Germanium

1. Introduction. Mn doped germanium was studied almost 60 years ago by means of Hall effect [1] and photo conductivity [2] measurements. Based on the temperature dependence of the resistivity and carrier concentration, two levels, one at 0.37eV from the conduction band and one at 0.16eV from the valence band have been assigned to Mn impurities[1]. In agreement with the valence bond model and similar observations by counterdoping with donors for Fe, Co and Ni, these impurities have been assigned to double acceptors. Moreover, the presence of a double acceptor level was confirmed by the observation of the Mn2- state with Electron Paramagnetic Resonance (EPR). [3] However it was also noted in the early studies that the presence of contamination with acceptor impurities may cast doubt on the charge transition assignment. Since the availability of Deep Level Transient Spectroscopy (DLTS), which is a more reliable technique to study deep levels in semiconductors, the electronic properties of most of the 3d transition metals have already been studied with a higher energy resolution. Metal in-diffusion was successful to introduce Cu and Ni[4]. More recently the defect levels of Ti, Cr, Fe and Co have been identified with DLTS on metal-implanted Ge [5,6]. The present study reports on results obtained on Mn doped Ge. 2. Experimental conditions. The source material are single crystal germanium wafers, supplied by Umicore, with a shallow dopant concentration of 1014 cm-3 Ga and Sb for p- and n-type, respectively. To introduce Mn impurities, 99.995% pure Mn was thermally evaporated on the Ge surface. Afterwards the specimens were placed in a resistive furnace under Ar atmosphere for 10 minutes at 700°C. Finally, the residual Mn on the surface was removed by etching with a mixture of HNO3 and HF (3:1?). Schottky diodes for DLTS were prepared by evaporation of Au (n-type) or In (p-type) barriers immediately after etching. To identify the contamination introduced during the processing, Schottky diodes were also prepared on parts of the specimens outside the Mn covered areas. Schottky diodes on n-Ge were also prepared by annealing the n-Ge:Mn samples (after indiffusion at 700°C) to 400°C for 20 min in order to form a MnGe metallic alloy contact. 3. Results and discussion. Fig. 1 a shows the DLTS spectrum of n-Ge:Mn with a MnGe Schottky contact. A similar spectrum was recorded on the specimen with an Au-Schottky barrier. Conventional DLTS shows one electron trap (Mn-E1), while injection of minority carriers (Vp>0) reveals two additional levels (Mn-H1 and Mn-H2). Fig. 1 b shows the DLTS spectrum of p-type Ge, with presence of Mn-H1 and Mn-H2 only after Mn diffusion.Figure 1: DLTS spectrum of a) n-Ge/MnGe diode. b) p-type Ge with and without Mn-difussion. The electron trap Mn-E1 (E=0.36eV) and the hole trap Mn-H1 (E=0.14eV) correspond with the two levels reported before [1,2]. The Mn-H2 peak (E=0.34eV) has to our knowledge not been reported before in the context of transition metal impurities. Nonetheless, its appearance only in Mn diffused samples, its almost equal amplitude and concentration profile to Mn-H1 suggests that it is also related to substitutional Mn in Ge. This may indicate that the substitutional Mn defect can adopt 4 charge states in Ge, one of which certainly corresponds with 2-, as identified with EPR. 4. Conclusions. Three Mn related defect levels have been identified with DLTS. The striking similarity with previously published results for two of the observed levels suggest the assignment to substitutional Mn in germanium. The third level was not reported before but can most probably also be assigned to Mn.

Design and modelling of high-operating temperature MWIR HgCdTe nBn detector with n- and p-type barriers

The paper present the numerical analysis of the electrical and optical properties of the mid-wave infrared (MWIR) HgCdTe nBn type detectors with a 3.4μm cut-off wavelength (at 50% of the initial rise in the response) operating at 230K. The analysed n+/B/n/N+ structure consists of four HgCdTe layers with n- and p-type barriers. Different structural parameters, as well as compositional and dopant profiles obtained in molecular beam epitaxy (MBE) and metal organic chemical vapour deposition (MOCVD) techniques were modelled with emphasis on conduction band and valence band-offset which determines the proper construction of the nBn type devices. The barrier must prevent the flow of the electron current from the cap region to the absorber while simultaneously ensure the flow and collection of thermally and optically generated holes from the absorber to the cap region. It was shown that proper p-type doping of the barrier reduce the valence band-offset and increase the offset in the conduction band leading to the optimal detector architecture.Theoretical results were related to the experimental data of the MWIR n+/B/n/N+ photodetectors grown by MOCVD. Dark currents of the first fabricated devices are limited by undesirable iodine diffusion from cap layer to the barrier. However, the nBn architecture might be a promising solution for HgCdTe infrared detectors grown by MOCVD, mainly due to the possibility of in situ acceptor doping of the barrier.

Schottky barrier height measurements of Cu/Si(001), Ag/Si(001), and Au/Si(001) interfaces utilizing ballistic electron emission microscopy and ballistic hole emission microscopy

The Schottky barrier heights of both n and p doped Cu/Si(001), Ag/Si(001), and Au/Si(001) diodes were measured using ballistic electron emission microscopy and ballistic hole emission microscopy (BHEM), respectively. Measurements using both forward and reverse ballistic electron emission microscopy (BEEM) and (BHEM) injection conditions were performed. The Schottky barrier heights were found by fitting to a linearization of the power law form of the Bell-Kaiser BEEM model. The sum of the n-type and p-type barrier heights are in good agreement with the band gap of silicon and independent of the metal utilized. The Schottky barrier heights are found to be below the region of best fit for the power law form of the BK model, demonstrating its region of validity.

Numerical Simulation and Analytical Modeling of InAs nBn Infrared Detectors with p-Type Barriers

This paper presents one-dimensional numerical simulations and analytical modeling of InAs nBn detectors having n-type barrier layers (BLs) with donor concentrations ranging from 1.8 × 1015 cm−3 to 2.5 × 1016 cm−3. We consider only “ideal” defect-free nBn detectors, in which dark current is due only to the fundamental mechanisms of Auger-1 and radiative recombination. We employ a simplified nBn geometry, with the absorber layer (AL) and contact layer (CL) having the same donor concentration and comparable thicknesses, to reveal more clearly the underlying device physics and operation of this novel infrared detector. We examine quantitatively the three space-charge regions in the nBn detector with an n-type BL, and determine a criterion for combinations of bias voltage and BL donor concentration that allow operation of the nBn with no depletion region in the narrow-gap AL or CL. We determine the quantitative characteristics of the valence band (VB) barrier that is present for an n-type BL but not for a p-type BL. Solving Poisson’s equation in the uniformly doped BL yields analytical expressions for the VB barrier height versus bias voltage, and an approximate expression for the crossover voltage for the onset of a depletion region in the AL. Our simulations lead to a new model for the ideal nBn with an n-type BL that consists of two ideal back-to-back photodiodes connected by a voltage-dependent series resistance representing the BL. Increasing the BL donor concentration lowers exponentially the mobile hole concentration in the BL, thereby exponentially increasing the BL series resistance. Reductions in dark current and photocurrent due to the valence barrier in the n-type BL only become appreciable when the BL series resistance becomes comparable to or exceeds the diffusion current resistances of the AL and CL.

The Semiconducting Properties and Impedance Analysis of Passive Films on Copper in Anoxic Sulfide-Containing Solutions from the Viewpoint of the Point Defect Model

The corrosion of pure copper in sulfide-containing aqueous solutions that are typical of crystalline rock repositories in Sweden and Finland for the isolation of High Level Nuclear Waste has been studied using potentiostatic and potentiodynamic polarization, Mott-Schottky analysis, and electrochemical impedance spectroscopy. The results, which are interpreted in terms of the Point Defect Model, indicate that a bi-layer sulfide film forms, comprising of a p-type barrier layer of Cu2S and probably an outer layer of CuS, which is n-type in electronic character. The outer layer is not observed to form at 25 oC and at 50 oC, but is observed to form intermittently at 75 oC. Thus, the outer layer is unstable and frequently disappears from the surface by sloughing, resulting in large excursions of the corrosion potential. This phenomenon is found to induce considerable instability in the electrochemical response of the system, such as that under potentiodynamic polarization.

Investigation of GaN-based dual-wavelength light-emitting diodes with p-type barriers and vertically stacked quantum wells

Designs of p-doped in quantum well (QW) barriers and specific number of vertically stacked QWs are proposed to improve the optical performance of GaN-based dual-wavelength light-emitting diodes (LEDs). Emission spectra, carrier concentration, electron current density, and internal quantum e±ciency (IQE) are studied numerically. Simulation results show that the e±ciency droop and the spectrum intensity at the large current injection are improved markedly by using the proposed design. Compared with the conventional LEDs, the uniform spectrum intensity of dual-wavelength luminescence is realized when a specific number of vertically stacked QWs is adopted. Suppression of electron leakage current and the promotion of hole injection e±ciency could be one of the main reasons for these improvements.

Comparison of nitride-based dual-wavelength light-emitting diodes with an InAlN electron-blocking layer and with p-type doped barriers

The advantages of nitride-based dual-wavelength light-emitting diodes (LEDs) with an InAlN electron blocking layer (EBL) are studied. The emission spectra, carrier concentration in the quantum wells (QWs), energy band and internal quantum efficiency (IQE) are investigated. The simulation results indicate that an LED with an InAlN EBL performs better over a conventional LED with an AlGaN EBL and an LED with p-type-doped QW barriers. All of the advantages are due to the enhancement of carrier confinement and the lower electron leakage current. The simulation results also show that the efficiency droop is markedly improved and the luminous intensity is greatly enhanced when an InAlN EBL is used.

Effect of P-Type Last Barrier on Efficiency Droop of Blue InGaN Light-Emitting Diodes

P-type doping in the last barrier is proposed to improve the efficiency droop of the blue InGaN light-emitting diodes (LEDs). The light-current curves, energy band diagrams, carrier concentrations, radiative recombination efficiency, and internal quantum efficiency of the blue LEDs under study are investigated. The simulation results show that the efficiency droop is significantly improved when the last undoped GaN barrier in a typical blue LED is replaced by a p-type GaN barrier. The simulation results suggest that the improvement in efficiency droop is mainly due to the decrease of electron current leakage and increase of hole injection efficiency.

Analysis of hopping conduction in semiconducting and metallic carbon nanotube devices

Single-walled carbon nanotube field-effect transistors were irradiated with 20 keV electrons using an e-beam lithography exposure method. Analysis of conduction data in the temperature range from 25 to 300 K indicated the creation of insulating regions containing traps along the nanotube channel. Further analysis of semiconducting and metallic nanotube devices shows dramatic differences in the effect of the electron exposure on the hopping defect barrier heights. Barriers for metallic nanotubes saturate at significantly larger values than semiconducting nanotubes due to shorter localization lengths. The limited and near constant density of states at the Fermi level induces a larger hopping length to localization length ratio, further limiting current and increasing measured trap heights. Poole–Frenkel hopping with an adjustment for electron localization is utilized to explain the inconsistencies. n-type and p-type barriers in the nanotube devices displayed exponential dependence on applied gate voltage bias, with the peak barrier height in the metallic device defining a switch of majority carrier.

ENHANCEMENT OF THE ELECTRONIC CONFINEMENT IMPROVES THE MOBILITY IN P-N-P DELTA-DOPED QUANTUM WELLS IN SI

The electronic structure and mobility trends in a n-type delta-doped quantum well in Si, matched between p-type delta-doped barriers of the same material, is presented. The distance between the n-type well and p-type barriers is varied from 50 A to 500 A; and also the impurity density from 5 × 1012 cm−2 to 5 × 1013 cm−2, for both, donors and acceptors. An increase in the mobility by a factor of 1.6 at interwell distance of 50 A with donor and acceptor concentrations of 5 × 1012 cm−2 and 5 × 1013 cm−2 compared with a single delta-doped well without p-type barriers is found. This improvement in mobility could be attributed to a better confinement of carriers, which favors excited levels with nodes in the donor plane. This trade-off between carrier concentration and mobility could be exploited in high-speed, high-power and high-frequency applications.