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Title of Thesis

Institute/University/Department Details
Department of Physics/ Quaid-i-Azam University Islamabad
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
transient spectroscopy, radiation-induced defects, silicon, semiconductors

A detailed study of deep-level defects introduced by energetic (5.48 MeV) alpha particles, in n- and p-type silicon is the primary theme of this thesis. Also included are the results of a follow-up study of the interaction of the radiation-induced defects with the deep-level defects in platinum-doped silicon. All the n- and p-type samples were one-sided junction diodes. These samples were exposed to a-particle doses up to 1.2 x l011 cm-2. Deep-level transient spectroscopy (DLTS) technique was used for the characterization of deep level defects. Emission rate signatures, activation energies, capture cross-sections with their temperature dependence, and defect concentrations and their spatial profiles for the detected deep levels were measured. Five electron levels and two hole levels were observed and characterized in detail in the as-irradiated n-silicon samples. In p-silicon samples, two hole levels and one electron levels emerged as a consequence of a-irradiation. A systematic study of generation rates of all the observed levels was performed providing insights into the dose dependence of their formation mechanism. Interesting room temperature transformation phenomena was observed in deep-level spectra during room temperature storage of the irradiated n-silicon samples. Similarly, in the irradiated p-silicon, some new features relating to temporal changes in the DLTS spectra stimulated by minority carrier injection were observed. Carrier Extensive isochronal annealing measurements were carried out to obtain data on annealing characteristics the of each of the radiation-induced deep levels. These measurements helped to identify these centres by comparison with the published data. A number of new annealed-in levels were observed during the investigation. The work on platinum-related levels in n-silicon consists of two parts -- a study of the possible temperature dependence of the electron capture cross-section of the pt-donor level in unirradiated si : pt and an investigation of the interaction of a-radiation with Pt-doped silicon. The interaction of a-radiation-induced levels with the Pt-related deep levels in Pt-doped n-silicon was studied by comparing the measured data for the levels in irradiated n-silicon and un irradiated Pt-doped n-silicon samples. Some interesting contrasts are seen to emerge on comparison our data with the published data of on electron-irradiated platinum-doped silicon.

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2420.91 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
168.07 KB
2 1 Introduction 1
63.66 KB
  1.1 Defects In Semiconductors 2
  1.2 Present Work-Motivation 4
  1.3 Scheme Of This Thesis 7
  1.4 References 8
3 2 General Properties And Defects In Silicon 9
95.62 KB
  2.1 General Properties Of Silicon 9
  2.2 Common Crystal Defects In Silicon 11
4 3 Historical Survey Of Radiation-Induced Defect Studies In Silicon 22
127.52 KB
  3.1 Introduction 22
5 4 Characterization Of Deep Levels (Some Theoretical Aspects) 38
309.34 KB
  4.1 Deep Level Parameters 38
  4.2 Carrier Kinetics In Semiconductors With Deep Levels €“ Shockley €“ Read And Hall (S-R-H) Theory 48
  4.3 Experimental Characterization Techniques 54
  4.4 Measurement Of Deep Level Characteristics By Dlts 67
6 5 Experimental Details 80
124.08 KB
  5.1 Instrumentation And Experimental Procedures 80
  5.2 Samples Preparation 89
  5.3 Irradiation Of Samples 93
7 6 A €“ Irradiated N-Type Silicon A. Results 97
364.31 KB
  6.1 Deep Level Spectra Of Unirradiated Silicon 97
  6.2 Electrical Characteristics After Irradiation 99
  6.3 Deep Level Spectra 102
  6.4 Electron Level E1 105
  6.5 Electron Level E2 110
  6.6 Electron Level E3 112
  6.7 Electron Level E4 116
  6.8 Electron Level E5 117
  6.9 Hole Level H1 118
  6.10 Hole Level H2 119
  6.11 Concentration Profiles 120
  6.12 Dlts Peak-Shape Profiles 122
  6.13 Annealing Characteristics 124
  6.14 Discussion 132
8 7 A €“ Irradiated P-Type Silicon 145
258.85 KB
  7.1 A. Results 145
  7.2 B. Discussion 172
9 8 Interaction Of Pt €“ Related Deep Level Defects With Alpha-Radiation And Capture Cross-Section Of Pt-Donor Level 180
265.13 KB
  8.1 A. Results 180
  8.2 B. Discussion 216
10 9 Conclusions 227
984.62 KB