Search query: impact ionization coefficient diamond

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abstract: Although a high breakdown voltage or field is considered as a major advantage of diamond, there has been a large difference in breakdown voltages or fields of diamond devices in literature. Most of these apparently contradictory results did not correctly reflect material properties because of specific device designs, such as punch through structure and insufficient edge termination. Once these data were removed, the remaining few results, including a record high breakdown field of 20 MV/cm, were theoretically reproduced, exactly calculating ionization integrals based on the ionization coefficients that were obtained after compensating for possible errors involved in reported theoretical values. In this compensation, we newly developed a method for extracting an ionization coefficient from an arbitrary relationship between breakdown voltage and doping density in the Chynoweth's framework. The breakdown field of diamond was estimated to depend on the doping density more than other materials, and accordingly required to be compared at the same doping density. The figure of merit (FOM) of diamond devices, obtained using these breakdown data, was comparable to the FOMs of 4H SiC and Wurtzite GaN devices at room temperature, but was projected to be larger than the latter by more than one order of magnitude at higher temperatures about 300 degC. Considering the relatively undeveloped state of diamond technology, there is room for further enhancement of the diamond FOM, improving breakdown voltage and mobility. Through these investigations, junction breakdown was found to be initiated by electrons or holes in a p type or n type drift layer, respectively. The breakdown voltages in the two types of drift layers differed from each other in a strict sense but were practically the same. Hence, we do not need to care about the conduction type of drift layers, but should rather exactly calculate the ionization integral without approximating ionization coefficients by a power function of electric field as often done in Si devices. In order to facilitate this approach, we developed a method for simplifying the ionization integral, which method, together with the aforementioned method for extracting ionization coefficients, will help to promote the study on breakdown phenomena of all semiconductors.
author_names: Atsushi Hiraiwa

Hiroshi Kawarada
title: Figure of merit of diamond power devices based on accurately estimated impact ionization processes
year: 2013

abstract: A general formalism has been developed for the calculation of band band Auger recombination and impact ionization rates in diamond and zinc blende type structures. The energy gap involved in the transition must be of order 1eV or greater, at room temperature, for direct gaps but is arbitrary for indirect gaps. A recombination coefficient of 28.1 x 10 32 cm6s 1 for GaP (hole hole electron collision) has been obtained in reasonable agreement with experiment. The formalism gives better theoretical values for Ge and Si than so far available. This has tended to reduce the recombination rates expected theoretically.
author_names: Dorothy Hill

Peter Landsberg
title: A formalism for the indirect Auger effect. I
venue: Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences
year: 1976

abstract: The avalanche photodiode is a highly sensitive photon detector with wide applications in optical communication and single photon detection. ZnO is a promising wide band gap material to realize a UV avalanche photodiode (APD) However, the lack of p type doping, the strong self compensation effect, and the scarcity of data on the ionization coefficients restrain the development and application of ZnO APD. Furthermore, ZnO APD has been seldom reported before. In this work, we employed a p Si/i ZnO/n AZO structure to successfully realize electron avalanche multiplication. Based on this structure, we investigated the band structure, field profile, Current Voltage (I V) characteristics, and avalanche gain. To examine the influence of the width of the i ZnO layer on the performance, we changed the i ZnO layer thickness to 250, 500, and 750 nm. The measured breakdown voltages agree well with the corresponding threshold electric field strengths that we calculated. The agreement between the experimental data and calculated results supports our analysis. Finally, we provide data on the impact ionization coefficients of electrons for ZnO along the (001) direction, which is of great significance in designing high performance low excess noise ZnO APD. Our work lays a foundation to realize a high performance ZnO based avalanche device.
author_names: Gaoming Li

Xiaolong Zhao

Xiangwei Jia

Shuangqing Li

Yongning He
title: Characterization of Impact Ionization Coefficient of ZnO Based on a p Si/i ZnO/n AZO Avalanche Photodiode
venue: Micromachines
year: 2020

abstract: A valanche multiplication characteristics in GaN p n junction diodes (PNDs) under high reverse bias conditions were investigated. The GaN on GaN PNDs with double side depleted shallow bevel termination, which showed low reverse leakage current and excellent avalanche capability, were used for the measurements. Under sub bandgap light illumination, the photocurrents induced by Franz Keldysh (FK) effect, which can be well reproduced by the theoretical calculations of the optical absorption, and their avalanche multiplications were observed. The multiplication factors were extracted as the ratios of the experimental photocurrents to the calculated FK induced photocurrent. Under an assumption of equal impact ionization coefficients of electrons and holes, the electric field dependence of an impact ionization coefficient in GaN were estimated.
author_names: Takuya Maeda

Tetsuo Narita

Hiroyuki Ueda

Masakazu Kanechika

Tsutomu Uesugi

Tetsu Kachi

Tsunenobu Kimoto

Masahiro Horita

Jun Suda
title: Estimation of Impact Ionization Coefficient in GaN by Photomulitiplication Measurement Utilizing Franz Keldysh Effect
venue: 2019 31st International Symposium on Power Semiconductor Devices and ICs (ISPSD)
year: 2019

abstract: This abstract presents an experimental study on the measurement of the hole impact ionization coefficient and saturation velocity in GaN. A novel p n structure with a buried p GaN was designed and demonstrated to have avalanche capability. Ultraviolet generated holes were swept into the high electric field region when the p n diode was reversely biased and triggered the hole initiated impact ionization multiplication. The measured hole saturation velocity is $7\times 10^{6} cm/s, and the impact ionization coefficient is \boldsymbol{\beta}\boldsymbol{E}=4.39\times 10^{6}\mathbf{exp} 1.8\times 10^{7}\boldsymbol{E}
author_names: Dong Ji

Burcu Ercan

Srabanti Chowdhury
title: Experimental Determination of Hole Impact Ionization Coefficient and Saturation Velocity in GaN
venue: 2019 Compound Semiconductor Week (CSW)
year: 2019

abstract: We report on the observation of ultrafast impact ionization in monocrystalline diamond driven by high intensity mid infrared femtosecond laser pulses. The measurements are based on monitoring the excited carrier population during and after the interaction of the pre excited sample with a strong infrared pulse by transient transmission spectroscopy and photoluminescence measurements. A twofold increase in the initial carrier population due to impact ionization is observed with the peak infrared intensity of 2.5 TW/cm2. The experimental results are supported by numerical simulations of electron dynamics using time dependent density functional theory, which show that the electrons in the conduction band reach the energy threshold for impact ionization during the interaction with the infrared pulse.
author_names: Martin Kozak

Michal Martinek

Tomohito Otobe

Frantisek Trojanek

Petr Maly
title: Observation of ultrafast impact ionization in diamond driven by mid infrared femtosecond pulses
year: 2020

abstract: This work exhibits a modified procedure to compute the electron impact ionization coefficient of silicon for temperatures between 77 and 800K and electric fields ranging from 70 to 400 kV/cm. The ionization coefficients are computed from the electron momentum distribution function through solving the Boltzmann transport equation (BTE) The arrangement is acquired by joining Legendre polynomial extension with BTE. The resulting BTE is solved by differences differential method using MATLAB(r) Six (X) equivalent ellipsoidal and non parabolic valleys of the conduction band of silicon are taken into account. Concerning the scattering mechanisms, the interval acoustic scattering, non polar optical scattering and II scattering are taken into consideration. This investigation showed that the ionization coefficients decrease with increasing temperature. The overall results are in good agreement with previous experimental and theoretical reported data predominantly at high electric fields.
author_names: M J Ahmed
title: Temperature dependence of electron impact ionization coefficient in bulk silicon
year: 2017

abstract: 97% des articles publies sur les etudes climatiques racontent que le rechauffement climatique est entierement cause par les activites humaines. Les gaz emis lors de la production d'energie electrique ainsi que d'autres gaz rejetes par les voitures ont un reel impact sur l'atmosphere. Une solution consiste a mettre au point des composants presentant des pertes de conduction plus faibles et des caracteristiques de claquage plus elevees qui pourraient etre utilises dans des centrales nucleaires, des cellules de commutation a haute puissance, des voitures hybrides (electriques) etc.De nos jours, les composants a base de silicium controlent environ 95% des dispositifs electroniques. Le carbure de silicium SiC et le nitrure de gallium GaN sont actuellement a l'etape de R&D, et commencent a etre integres dans certains circuits electroniques. D'autres materiaux tels que Ga2O3, AlN ou le diamant sont encore a l'etape de recherche. Les derniers sont connus sous le nom de materiaux a bande ultra large et semblent etre la solution requise pour les faibles pertes de puissance. Le diamant est reconnu comme le materiau ultime pour la prochaine generation de composants de puissance en raison de ses proprietes physiques exceptionnelles telles qu'un champ de claquage eleve >10 MV/cm) permettant d'utiliser le dispositif pour une commande de puissance elevee, une mobilite de porteurs elevee (2 000 cm^2/V.s pour les trous) une vitesse de saturation elevee, une conductivite thermique elevee (22 W/cm.K) pour une parfaite dissipation de chaleur et une faible constante dielectrique. Theoriquement, le diamant est le semi conducteur offrant le meilleur compromis entre resistance a l'etat passant et tension de claquage. En particulier, en raison de l'ionisation incomplete des dopants, il est encore plus efficace a haute temperature. Diverses diodes Schottky en diamant (SBD) avec de bonnes performances a l'etat passant et bloque (7,7 MV/cm) ont ete rapportees. En plus des SBDs, des transistors a effet de champ (FET) ont egalement ete etudies a travers des oxyde metal semi conducteur FETs (MOSFETs) utilisant une surface hydrogenee avec des densites de courant elevees a l'etat passant ou des surface oxygene avec de bonnes caracteristiques de blocage. Pour les composants de haute tension, il est necessaire de changer l'architecture de l'electrode afin d'eviter un claquage premature due a l'encombrement du champ electrique aux bords. Dans ce but, les techniques de terminaison de bord sont utilisees pour atteindre les caracteristiques ideales. La tache evidente avant toute fabrication de composant est la partie simulation qui predit l'optimisation de l'architecture et les caracteristiques attendues. Une bonne prediction necessite la connaissance des parametres du materiau. Les parametres importants pour le claquage sont les coefficients d'ionisation par impact. Plusieurs coefficients ont ete publies pour le diamant. Toutefois, ils ont ete extraits en fittant des structures non optimisees, d'ou un manque de precision.Dans cette etude, deux structures de terminaisons de bord pour des diodes Schottky, appelees plaque de champ et anneaux a champ flottant, ont ete etudiees. Leur efficacite de distribution du champ de surface par analyse de courant induit par faisceau d'electrons (EBIC) a ete observee. De plus, des FETs ont ete fabriques et caracterises, un MESFET et un RB MESFET. Les FETs presentent un claquage eleve, jusqu'a 3 kV et une faible resistance. Le developpement des transistors est indissociable de la diode Schottky, car ils sont tous deux necessaires a la fabrication de cellules de commutation. Et enfin, les coefficients d'ionisation par impact pour les electrons ont ete mesures a l'aide d'EBIC pour un champ >0,5 MV/cm dans une region sans defaut. Les valeurs mesurees sont (sous l'equation de Chynoweth) an 971 /cm et bn=2,39x10^6 V/cm. Ces valeurs sont proches des coefficients mesures experimentalement et rapportes dans la litterature.
author_names: Khaled Driche
title: Diamond unipolar devices towards impact ionization coefficients extraction
year: 2018

abstract: Diamond has the advantage of having an exceptionally high critical electric field owing to its large band gap, which implies its high ability to withstand high voltages. At this maximum electric field, the operation of Schottky barrier diodes (SBDs) as well as FETs, may be limited by impact ionization, leading to avalanche multiplication, and hence the devices may breakdown. In this study, three of the reported impact ionization coefficients for electrons, an, and holes, ap, in diamond at room temperature (300 K) are analyzed. Experimental data on reverse operation characteristics obtained from two different diamond SBDs are compared with those obtained from their corresponding simulated structures. Owing to the crucial role played by the impact ionization rate in determining the carrier transport, the three reported avalanche parameters implemented affect the behavior not only of the breakdown voltage but also of the leakage current for the same structure.
author_names: Khaled Driche

H Umezawa

Nicolas Rouger

Gauthier Chicot

Etienne Gheeraert
title: Characterization of breakdown behavior of diamond Schottky barrier diodes using impact ionization coefficients
year: 2017

abstract: Electron impact ionization coefficient a is one of the most important parameters used in the study of gas discharge.However,the a values usually determined in the experiments on Townsend discharge in gases at low pressure are not applicable to the gas discharges in atmospheric gases.Aiming at solving this problem,a method for determining the a values in the gases at atmospheric pressure was proposed.Dielectric barrier Townsend discharges were produced in some gases at atmospheric pressure.The distribution of the light intensity in the discharge gap was recorded by taking side view photograph using an ICCD camera with an extremely short exposure time and compared with the theoretical distributions with different presumed a.The a value was determined by the best fitting of the theoretical distribution to the experimental one.The method was proved to be applicable in the determination of a for nitrogen at atmospheric pressure.
author_names: Wang Xinxin
title: Preliminary Measurement of Electron Impact Ionization Coefficient in Gases at Atmospheric Pressure
year: 2012