Andrei Sazonov

Associate Professor

Electrical and Computer Engineering Department

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ECE 639 "Physics and Applications of Amorphous Silicon"

Outline:

1.

Introduction:

  • comparison of c-Si, poly-Si, nc-Si, and a-Si:H in terms of electronic properties, fabrication cost, deposition limitations and application areas;

  • special features and inherent limits of each material;

  • a-Si:H, poly-Si, nc-Si step-by-step review: growth, structure, states, doping, transport, applications.

1 hr

2.

Growth:

  • deposition techniques;

  • growth process;

  • thin films growth;

  • process windows and process parameter control.

2 hrs

3.

Structure:

  • An introductory review: SRO, MRO, LRO;

  • SRO: RDF, strained bonds, stress, defect formation;

  • MRO: voids, stress, overcoordination;

  • LRO: crystallinity, amorphous tissue;

  • phonons, Raman, a-Si and mc-Si;

  • hydrogen in silicon: bonding, FTIR, trapping and effusion, DSC;

  • the role of hydrogen.

3 hrs

4.

Electronic states:

  • extended and localized states, Anderson’s localization;

  • a-Si:H bandgap structure, bandgap models;

  • band tails, density of states measurements;

  • Urbach energy, Tauc plot.

2 hrs

5.

Defects:

  • defects in c-Si and in a-Si;

  • defect charge states in a-Si:H, charge transfer;

  • electron spin resonance;

  • defect energy measurements.

1 hr

6.

Doping:

  • doping mechanisms in c-Si, mc-Si, and a-Si:H;

  • doping efficiency;

  • relationship between the doping and defects;

  • doping models.

3 hrs

7.

Metastability:

  • stable and metastable states, equilibration;

  • relationship between the structure and metastability: models and experiments;

  • metastability and electronic properties;

  • metastable effects in a-Si:H (Staebler-Wronski effect, threshold voltage shift, particle bombardment, doping efficiency change).

1 hr

8.

Electronic transport:

  • types of conductivity in c-Si, mc-Si, and a-Si:H;

  • transport through extended, localized, and defect states;

  • temperature dependence, Meyer-Neldel rule;

  • carrier mobility.

2 hrs

9.

Interfaces and contacts:

  • Schottky contacts, ohmic contacts;

  • interface defects, their measurements;

  • relationship between the structure, material quality, and the interface states;

  • interfaces with doped layers, nitrides, and oxides.

3 hrs

10.

Poly-Si, mc-Si, nc-Si, pc-Si and pm-Si - structurally inhomogeneous silicon films:

 deposition, structure, doping, electronic properties, applications.

3 hrs

11.

Applications: solar cells:

  • physical principles;

  • energy conversion losses;

  • device structures;

  • performance characterization;

  • different materials for solar cells.

3 hrs

12.

Applications: displays:

  • different types of displays; 

  • liquid crystal displays: physical basics; 

  • passive matrix and active matrix displays.

3 hrs

13.

Applications: imaging:

  • physical basics of imaging;

  • visible, IR, UV, and x-ray imaging, color recognition;

  • device structures and fabrication.

3 hrs

14.

Applications: macroelectronics:

  • the concept of macroelectronics;

  • consumer electronics and disposable electronics;

  • flexible electronics;

  • “sensitive skin” and “smart clothes”;

  • biomedical sensors and systems.

3 hrs

15.

Course project presentation.

3 hrs