Physical charateristics and applications of nanometer thin boron-on-silicon layers in silicon detector devices

doctoral thesis

• Title (croatian): Fizikalne karakteristike i primjena nanometarski tankih slojeva bora na siliciju u silicijskim detektorima
• Author: Tihomir Knežević
• Mentor: Tomislav Suligoj (mentor)
• Committee member: Tomislav Suligoj (predsjednik povjerenstva)
• Granter: University of Zagreb; Faculty of Electrical Engineering and Computing; (Department of Electronics, Microelectronics, Computer and Intelligent Systems); Zagreb
• Defense date and country: 2017, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Electrical Engineering; Electronics
• Universal decimal classification (UDC): 621.3 - Electrical engineering

Abstract

Deposition of ultra-thin pure amorphous boron (PureB) layers directly on silicon have in recent years been used to fabricate various types of silicon detector devices that have I-V characteristics with ideality factor equal to 1 and low dark currents together with excellent responsivity, stability and robustness. In this thesis, PureB layers were examined with material characterization techniques such as X-ray photoemission spectroscopy and spectroscopic ellipsometry. An extensive electrical characterization is performed on devices with PureB layers at temperatures from room temperature down to 77 K in a cryogenic liquid nitrogen system, which provided an understanding of the carrier transport across the PureB-silicon interface and conduction through the PureB layers. The main mechanism for carrier conduction through the PureB layer was identified as variable range hopping conduction. For ultra-thin PureB layers with thickness lower than 2 nm, the holes can tunnel to an aluminum contact ordinarily used on PureB layers. An interfacial hole layer at the PureB/Si interface was found to be able to account for the effective blocking of electron injection from the bulk. The information gathered on the physical and electrical characteristics of the PureB-on-silicon layers was used to develop an electrical model of the PureB layer and its interface with silicon. Incorporation of the thus defined model in technology computer aided design (TCAD) software provided an efficient tool for proposing and simulating novel photodiode structures integrating PureB layers to exploit the attractive electrical and optical characteristics. A detailed TCAD analysis was performed on guard ring optimization of PureB devices, optimization of PureB single photon avalanche diode (SPAD) geometry, reduction of indirect optical crosstalk in a SPAD array, and novel silicon drift detectors with the drift field induced by PureB-coated trenches.

Abstract (croatian)

Depozicija ultra-tankih slojeva čistog amorfnog bora (PureB) direktno na silicijsku podlogu upotrijebljena je za proizvodnju različitih silicijskih poluvodičkih elemenata koji imaju I-U karakteristike s faktorom idealnosti 1 i nisku tamnu struju uz izvrsnu osjetljivost, stabilnost i robusnost. U ovoj doktorskoj disertaciji, PureB slojevi su analizirani metodama karakterizacije poput spektroskopije s foto-emisijom X-zraka i spektroskopske elipsometrije. Iscrpna električka karakterizacija napravljena je na poluvodičkim elementima s PureB slojevima pri temperaturama od sobne do 77 K koja karakterizira sustav s tekućim dušikom čime je identificiran transport nosilaca kroz PureB sloj i preko PureB-silicijskog međuspoja. Glavni mehanizam transporta kroz PureB sloj odvija se vođenjem s varijabilnim skokovima (variable range hopping conduction). Za ultra-tanke PureB slojeve s debljinama manjim od 2 nm, šupljine mogu tunelirati do aluminijskog kontakta koji se uobičajeno koristi na PureB slojevima. Efektivno blokiranje struje elektrona iz podloge omogućeno je slojem šupljina na PureB/Si međuspoju. Informacije o fizikalnim i električkim karakteristikama slojeva PureB-a na siliciju su iskorištene za razvoj električkog modela PureB sloja i međuspoja sa silicijem. Navedeni model iskorišten je u TCAD softwareu za simuliranje poluvodičkih elemenata (TCAD - technology computer aided design) pomoću kojega je moguće predlagati i simulirati nove strukture fotodioda koje omogućavaju integraciju PureB slojeva u svrhu iskorištenja atraktivnih električkih i optičkih karakteristika tog sloja. Detaljna TCAD analiza napravljena je na: optimizaciji zaštitnih prstenova elemenata s PureB slojevima; optimizaciji geometrije dioda s mogućnošću detekcije jednog fotona temeljenoj na lavinskoj multiplikaciji (SPAD - single photon avalanche diode); smanjivanju indirektnog optičkog preslušavanja kod SPAD nizova; novim drift detektorima s driftnim poljem definiranim pomoću žljebova prekrivenih PureB slojem.

• Keywords: PureB; material characterization; X-ray photoemission spectroscopy; XPS; spectroscopic ellipsometry; electrical characterization; low-temperature measurements; PureB model; variable range hopping conduction; tunneling; guard ring optimization; perimeter effects; single photon avalanche diodes; SPAD; SPAD array; dark count rate modeling; 2D DCR modeling; indirect optical crosstalk reduction; drift detectors
• Keywords (croatian): PureB; karakterizacija materijala; fotoemisija X-zrakama; XPS; spektroskopska elipsometrija; električka karakterizacija; nisko-temperaturna mjerenja; PureB model; tuneliranje; optimizacija zaštitnih prstenova; periferni efekti; detektori za detekciju jednog fotona temeljenih na lavinskoj multiplikaciji; SPAD; modeliranje brzine generacije tamnih impulsa; DCR; 2D DCR; indirektno optičko preslušavanje; drift detektori.
• Language: english
• URN:NBN: urn:nbn:hr:168:731738
• Study programme: Title: Electrical Engineering and Computing; Study programme type: university; Study level: postgraduate; Academic / professional title: Doktor znanosti elektrotehnike i računarstva (Doktor znanosti elektrotehnike i računarstva)
• Type of resource: Text
• Extent: 210 str. ; 30 cm.
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2019-04-04 13:05:34