Planar Schottky Barrier Diode Research Articles

Different reverse leakage current transport mechanisms of planar Schottky barrier diodes(SBDs) on sapphire and GaN substrate

The effects of different substrates on the off-state leakage current in gallium nitride (GaN) planar diodes are experimentally demonstrated and studied by analyzing temperature-dependent current–voltage characteristics. The two devices exhibit different leakage mechanisms despite being subjected to the same process conditions. The device with a sapphire substrate shows a more intricate leakage mechanism, implying the presence of additional leakage channels compared to the device with free-standing substrates. The electrical leakage characteristics in the planar GaN-on-sapphire device (referred to as utemp-SBD) and GaN substrate device (referred to as usub-SBD) Schottky barrier diodes (SBD) can be described by two distinct processes as the reverse bias gradually increases: utemp-SBD go through the thermionic emission (TE), variable range hopping (VRH), Frenkel–Poole (FP) emission and space-charge-limited conduction (SCLC) model; The leakage conduction mechanism of usub-SBD include TE, VRH, and FP emission mechanisms. It is noteworthy that in device 1, there is a rapid increase in leakage current within the voltage range of −36 to −40 V, primarily driven by the SCLC mechanism. This effect arises due to the presence of intrinsic traps in GaN grown on a heterogeneous substrate. Additionally, in the voltage range of −7 to −50 V (348 K to 448 K), the leakage mechanism shifts from FP emission to the VRH model, possibly due to variations in the Schottky barrier height.This study provides an in-depth analysis of the leakage mechanisms observed on different substrates and offers valuable insights for the design of planar gate transistors to minimize or avoid the occurrence of leakage channels.

Monolithic integrated GaN-based 120 GHz frequency doubler on sapphire

In this work, a novel monolithic integrated frequency doubler in D-band was designed and fabricated on sapphire substrate. A 120 GHz solid-state source gallium nitride (GaN) planar Schottky barrier diode (SBD) chain integrating with microstrip circuitry was achieved and analyzed. The continuous mode output power of the prototype device reaches 35.6 mW at 120 GHz with an efficiency of 8.9%. The characteristics of GaN SBDs and monolithic integrated heat dissipation are discussed and analyzed. Our results announce the success of exploring a novel avenue toward frequency multipliers in GaN materials solid-state sources, which greatly simplifies the assembly, and improves assembly accuracy and the scale of integration possible for terahertz applications.

Analysis of electrical properties in lateral Schottky barrier diode based on n-GaN and AlGaN/GaN heterostructure

In this paper, the lateral Schottky barrier diodes (SBDs) with small capacitance and low turn-on voltage (Von) were fabricated on n-GaN and AlGaN/GaN heterostructure. The capacitances of lateral n-GaN SBD and lateral AlGaN/GaN SBD are 1.35 pF/mm and 0.70 pF/mm, respectively. Compared with the planar SBDs, the capacitances of lateral SBDs are reduced by about two orders of magnitude without sacrificing the performance of on-resistance (Ron) and reverse leakage current. For the planar and lateral n-GaN SBDs, the value of the Von is similar. However, compared with the planar AlGaN/GaN SBD, the Von of lateral AlGaN/GaN SBD is reduced from 1.64 V to 0.87 V owing to the anode metal directly contacting the two-dimensional electron gas. According to temperature-dependent I-V results, the barrier inhomogeneity of the lateral SBD is more intensive than the planar SBD, which is attributed to etching damage. The withstand voltage of SBD is a very important parameter for power electronic applications. Compared with the breakdown voltage of 73 V in the lateral n-GaN SBD, the lateral AlGaN/GaN SBDs exhibit a breakdown voltage of 2322 V. In addition, we found that Schottky contact introduces anode resistance (RA) by analysing the Ron distribution of lateral SBDs. The experimental results also show that the RA of lateral n-GaN SBD and lateral AlGaN/GaN SBD are 10.5 Ω mm and 9.2 Ω mm respectively, which are much larger than the ohmic contact resistance due to worsening anode contact by metal-induced gap states.

High-Efficiency D-Band Monolithically Integrated GaN SBD-Based Frequency Doubler With High Power Handling Capability

A high-efficiency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D}$ </tex-math></inline-formula> -band monolithically integrated GaN frequency doubler based on a pair of antiseries four-anode planar GaN Schottky barrier diodes (SBDs) has been successfully fabricated. Unlike the traditional hybrid integrated circuit technology, the monolithic integrated circuit technology has been used in the design and fabrication of GaN SBD-based frequency doubler circuits to achieve good alignment and low conversion losses. At room temperature, the experiments show that the peak conversion efficiency reaches 17.0% at 115.6 GHz under a continuous wave (CW) driving which is a critical requirement for many practical applications. The efficiency of 17.0% is the highest efficiency of GaN SBD-based multipliers at present under CW driving mode. This monolithically integrated doubler also exhibits a broadband high efficiency characteristic of more than 4.7% (−5.58 dB from 17%) across a 10% band from 109 to 121 GHz. In addition, high CW power handling capability of the proposed frequency doubler is verified. The experiments show that the frequency doubler can endure a maximum CW input power of 0.5 W.

The Development of Frequency Multipliers for Terahertz Remote Sensing System

This paper summarizes the development of novel Schottky-diode-based terahertz frequency multipliers. The basic structure and manufacturing process of planar Schottky barrier diodes (SBDs) are reviewed, along with other diode structures that have been proposed in the literature. A numerical modeling method for the novel diodes in the context of terahertz frequency multipliers is presented, which includes 3D electromagnetic (EM) modeling, electro-thermal modeling and modeling of physical non-ideal effects. Furthermore, a general design methodology for developing terahertz frequency multipliers is introduced, involving a sub-division design method (SDM), a global design method (GDM) and a half-sub-division and half-global design method (HS-HGDM). These methods are summarized and compared for 110 GHz and 220 GHz frequency multipliers in the context of communication and imaging applications. Laboratory measurements of these multipliers show good agreement with numerical simulations. Finally, several classic terahertz remote sensing systems are reviewed, and a 220 GHz remote sensing system established using novel frequency multipliers for security inspection purposes is presented along with associated imaging results.

Multi-channel AlGaN/GaN Schottky barrier diodes with a half through-hole

The cutoff frequency of Schottky barrier diode (SBD) depends on its junction capacitance and series resistance. The two-dimensional electron gas (2DEG) at AlGaN/GaN interface has high carrier mobility and carrier concentration. However, AlGaN/GaN heterostructure SBD usually shows a high series resistance because of the thin 2DEG channel. In this work, multiple AlGaN/GaN heterojunctions are vertically stacked for forming multiple parallel 2DEG channels to reduce the series resistance. Multi-channel AlGaN/GaN-based air-bridge structure planar SBDs with a half through-hole are demonstrated. The series resistance of quintuple-channel SBD is only 39.5% of the single-channel SBD's. Moreover, a low capacitance is obtained by the Schottky electrode with a half through-hole structure. The low series resistance and the low capacitance contribute to a 16 GHz cutoff frequency in millimeter-wave band.

Advances of beveled mesas for GaN-based trench Schottky barrier diodes

In this article, we propose and investigate a GaN-based trench metal–insulator–semiconductor barrier Schottky rectifier with a beveled mesa and field plate (BM-TMBS). According to our study, the beveled mesa and field plate structures help to reduce the density of potential lines at the mesa corner and deplete the drift region in two-dimensional mode, respectively. By doing so, the electric field at the bottom corner of the trenches and Schottky contact/GaN interface can be decreased significantly and the breakdown voltage can also be improved remarkably when compared with the conventional TMBS rectifiers and the planar Schottky barrier diodes. Meanwhile, assisted by the beveled mesa structure, the improved current spreading effect and a better conductivity modulation can be obtained in the forward-conduction state. Our studies also show that the electric field profiles and charge-coupling effect can be influenced by the mesa angle, the insulating layer thickness (Tox), and the trench depth (Dtr). As a result, the optimized BM-TMBS rectifiers can obtain a high BV of ∼2 kV and a current density of ∼3 kA/cm2 at the forward bias of 2 V.

Design Guidelines for Recessed Schottky Barrier AlN/GaN Diode for THz Applications

In this work, we have explored the design space for multifinger planar Schottky barrier diodes (SBDs) using AlN/GaN heterostructure for terahertz (THz) applications. Using a well-calibrated computational modeling framework, we have identified the critical design parameters and associated parasitic elements affecting diode's THz performance. The 3-D modeling of parasitics components has been deployed as the 2-D design approach overestimates the performance or underestimates the parasitic components in a multifinger design. Device design guidelines and the tradeoff between various parameters are discussed in detail. The optimum design space and related tradeoffs were found to be nonintuitive due to the presence of 3-D parasitics capacitances and resistances.

Design of 220GHz harmonic mixer

220GHz is the frequency of atmospheric window. The mixer working in this frequency band has a very important application in terahertz communication detection and other fields. This paper introduces a mixer design based on planar Schottky barrier diode. Based on the reverse parallel diode fabricated by the process platform of the 13th Research Institute of China Electronics Technology Group Corporation. The schematic layout of the mixer is simulated and optimized by the joint design of ADS and HFSS and other electromagnetic simulation software. Finally, The frequency conversion loss is less than 9 in the range of 200 to 240 RF frequencies.

Low capacitance AlGaN/GaN based air-bridge structure planar Schottky diode with a half through-hole

The capacitance and the series resistance are two main factors which determine the cut-off frequency of Schottky barrier diodes (SBDs) for their application in millimeter-wave and terahertz regions. The junction capacitance is closely related to the anode dimension of a SBD. Reducing the anode size can effectively decrease the junction capacitance, but it will increase the series resistance and the difficulty of the device manufacturing process is also increased. In this paper, an AlGaN/GaN based air-bridge structure planar SBD with a half through-hole is investigated. The half through-hole was formed on the center of a circular anode by inductively coupled plasma etching to the unintentional doping-GaN channel layer. The capacitance formed by the anode metal and the two-dimensional electron gas at the AlGaN/GaN interface is effectively reduced under the condition of holding the metal area of anode. The total capacitance of the 20 μm-radius anode SBD with a 19.95 μm-radius half through-hole dramatically decreases from 2.32 pF of the device without the half through-hole to 21.5 fF. In addition, since the current is mainly distributed at the edge of the circular anode, the series resistance is only slightly increased. The cut-off frequency of the air-bridge planar SBD with a 20 μm-radius anode and a 19.95 μm-radius half through-hole was 114.1 GHz. To reduce the size of the anode and optimize the ohmic contact, the cut-off frequency could be further improved.

Dual Lumped Ports Technique and Its Applications in Modeling of Planar Schottky Diode in THz Band

Micro-coaxial probe technique (MCPT) is widely used in three-dimensional electromagnetic (3-D EM) modeling of planar Schottky barrier diodes (SBDs) for the design of terahertz multipliers and mixers. However, the inconsistency of port numbers between 3-D EM model and intrinsic model of diode has been pended for years due to the lack of alternative internal port techniques. In this paper, after investigating port techniques available for field simulation software, a novel dual lumped ports technique (DLPT) is proposed to replace the MCPT for removing its non-physical grounding requirement, which makes the defined internal ports have definite physical meaning. Moreover, the proposed DLPT possesses higher accuracy than MCPT for the elimination of epitaxial layer penetration and additional consideration of port coupling effect. Detail technical procedures for DLPT are presented for internal double ports implementation. To verify its feasibility and accuracy at terahertz band, a 110 GHz broadband tripler was designed utilizing the proposed DLPT and the measured results agree well with the simulated ones. Furthermore, a series of frequency multipliers designed by MCPT are post-analyzed with the same models derived from DLPT. Finally, a slight discrepancy is observed between MCPT and DLPT, and the latter coincides better with the measured results. All these results indicate that the proposed DLPT is validated to be effective and accurate for the design of diode frequency multipliers and mixers in terahertz region.

Fast-Switching Tri-Anode Schottky Barrier Diodes for Monolithically Integrated GaN-on-Si Power Circuits

Tri-Anode GaN Schottky Barrier Diodes (SBDs) have recently shown excellent DC performance with low turn-on voltage and large breakdown thanks to their 3D contact structure around the two-dimensional electron gas (2DEG) channel. However, the 3D nature of the Tri-Anode structure is also often believed to hinder the device switching performance. In this work, we demonstrate that, on the contrary, the Tri-Anode architecture significantly enhances the device switching performance with respect to conventional planar SBDs, as shown by a substantial decrease in the recovery charge and an improvement in frequency response. The Tri-Anode SBDs excellent static and dynamic performance is then applied to a real circuit to demonstrate a monolithically integrated high-frequency Full Bridge Rectifier. These results show the potential of Tri-Anode SBDs for high-efficiency and fast-switching power integrated circuits.

A Novel 220-GHz GaN Diode On-Chip Tripler With High Driven Power

This letter presents our study on a high power 220 GHz frequency tripler based on a pair of GaN planar Schottky barrier diode chain chips. In the proposed frequency tripler, the pair of diode chips was directly mounted across the metal diaphragm in parallel with the opposite polarisation inside the rectangular waveguide. The RF field is tuned to its hot-spot, coupling directly onto the diode chains, turning on a diode chain at a time in an alternative manner. Unlike the traditional ones, in order to achieve better heat dissipation, the diodes are directly connected with the metal block. Benefitting from a better heat dissipation and the power endurance capacity of GaN material, the proposed tripler can work well under a watt level input power. The simulated tripler frequency conversion performance agrees with the measurement results very well. In addition, the experiments show that the frequency tripler can endure a maximum input power of 1.1W. In addition, the output power of this frequency tripler is 17.5mW at 219.5GHz driven by 900mW input power with the best efficiency of 1.93%.

Monte Carlo Study of 2-D Capacitance Fringing Effects in GaAs Planar Schottky Diodes

Nanometer scale planar Schottky barrier diodes (SBDs) with realistic geometries have been studied by means of a 2-D ensemble Monte Carlo simulator. The topology of the devices studied in this paper is based in real planar GaAs SBDs used in terahertz applications, such as passive frequency mixing and multiplication, in which accurate models for the diode capacitance are required. The intrinsic capacitance of such small devices, which due to edge effects strongly deviates from the ideal value, has been calculated. In good agreement with the classical models, we have found that the edge capacitance is independent of the properties of the semiconductor beneath the contact and, as novel result, that the presence of surface charges at the semiconductor dielectric interface can reduce it almost 15%. We have finally provided a compact model for the total capacitance of diodes with arbitrary shape that could be easily implemented in design automation software such as Advance Design System (ADS).

GaN planar Schottky barrier diode with cut‐off frequency of 902 GHz

GaN planar Schottky barrier diode (SBD) with an n−/n+ structure was grown and fabricated on sapphire substrate. An n+ GaN epitaxial layer with doping concentration of 8 × 1018 cm−3 was employed to reduce the parasitic resistance. An air-bridge structure and 50 μm substrate thinning-down technique were adopted in order to reduce the parasitic capacitance. A record cut-off frequency (f c) of 902 GHz was achieved for GaN planar SBD with 2 μm anode diameter.

A 220 GHz frequency tripler based on 3D electromagnetic model of the schottky diode and the field-circuit co-simulation method

In this article, a 220 GHz frequency tripler using three-dimensional (3D) electromagnetic simulation is designed. Due to the characteristics of extremely short working wavelength and ultra-small circuit size of terahertz frequency multipliers, complicated parasitic effect cannot be ignored, which leads to a limited optimization space for circuit matching in the design of terahertz components. In this article, a precise 3D electromagnetic (EM) model of the planar Schottky barrier diode (SBD) is established and the field-circuit co-simulation method is proposed for the design of the 220 GHz tripler. Compared with the varistor diode, the frequency multiplier based on the varactor diode will produce higher output power due to its lossless mechanism. The measured results show that the output power is higher than 5 mW in the frequency range 220∼228 GHz, with the maximum output power of 6.34 mW. Typical conversion loss is 15 dB in the frequency range 216∼232 GHz. The frequency tripler has the characteristics of compact size, low loss, and high output power. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1647–1651, 2016

The Study of 0.34 THz Monolithically Integrated Fourth Subharmonic Mixer Using Planar Schottky Barrier Diode

A planar Schottky barrier diode with the designed Schottky contact area of approximately 3 μm2 is developed on gallium arsenide (GaAs) material. The measurements of the developed planar Schottky barrier diode indicate that the zero-biased junction capacitance Cj0 is 11.0 fF, the parasitic series resistance RS is 3.0 Ω, and the cut off frequency fT is 4.8 THz. A monolithically integrated fourth subharmonic mixer with this diode operating at the radio frequency (RF) signal frequency of 0.34 THz with the chip area of 0.6 mm2 is implemented. The intermediate frequency (IF) bandwidth is from DC to 40 GHz. The local oscillator (LO) bandwidth is 37 GHz from 60 to 97 GHz. The RF bandwidth is determined by the bandwidth of the on chip antenna, which is 28 GHz from 322 to 350 GHz. The measurements of the mixer demonstrated a conversion loss of approximately 51 dB.

Electrical activity of (100) n‐type diamond with full donor site incorporation of phosphorus

In a previous work, we discovered a new set of growth parameters for fabricating (100) homoepitaxial phosphorus‐doped n‐type diamond with unique properties: full incorporation of phosphorus donors in substitutional sites together with a low surface roughness. In this work, a planar type Schottky barrier diode has been fabricated on the epilayer and C–V characteristics were measured. From the capacitance properties, the net donor density and the Schottky barrier height were experimentally determined to be ∼3.1 × 1016 cm−3 and ∼4.65 eV, respectively. The phosphorus electrical activity in our (100) n‐type diamond epilayer is discussed in comparison with previous works on the (100) and (111) orientations.

Breakdown characteristics of AlGaN/GaN Schottky barrier diodes fabricated on a silicon substrate

In this work, the breakdown characteristics of AlGaN/GaN planar Schottky barrier diodes (SBDs) fabricated on the silicon substrate are investigated. The breakdown voltage (BV) of the SBDs first increases as a function of the anode-to-cathode distance and then tends to saturate at larger inter-electrode spacing. The saturation behavior of the BV is likely caused by the vertical breakdown through the intrinsic GaN buffer layer on silicon, which is supported by the post-breakdown primary leakage path analysis with the emission microscopy. Surface passivation and field plate termination are found effective to suppress the leakage current and enhance the BV of the SBDs. A high BV of 601 V is obtained with a low on-resistance of 3.15 mΩ·cm2.

A New Resistance Model for a Schottky Barrier Diode in CMOS Including N-well Thickness Effect

A new resistance model for a Schottky Barrier Diode (SBD) in CMOS technology is proposed in this paper. The proposed model includes the n-well thickness as a variale to explain the operational behavior of a planar SBD which is firstly introduced in this paper. The model is verified using the simulation methodology ATLAS. For verification of the analyzed model and the ATLAS simulation results, SBD prototypes are fabricated using a 0.13㎛ CMOS process. It is demonstrated that the model and simulation results are consistent with measurement results of fabricated SBD.