ECE 874: Physical Electronics Prof. Virginia Ayres Electrical & Computer Engineering Michigan State University ayresv@msu.edu

Lecture 01, 30 Aug 12 VM Ayres, ECE874, F12

Chp. 01: Basic Semiconductor Properties Crystal structures Motivation VM Ayres, ECE874, F12

Motivation: nanoFET with large current density J VM Ayres, ECE874, F12

Motivation: C and D: selected area electron diffraction A, B, and E: High resolution transmission electron microscopy VM Ayres, ECE874, F12

Figure 1.1: VM Ayres, ECE874, F12

Top way might seem easier Figure 1.1: Bottom way VM Ayres, ECE874, F12

In a real problem where you don’t know a and b distances or how to set the lines “in-between”, bottom way would be easier VM Ayres, ECE874, F12

Another point: This is a 2D plane view of a 3D crystal VM Ayres, ECE874, F12

Figure 1.2: When describing crystals, we do it this way. These lines and even points describe symmetries not bonds. VM Ayres, ECE874, F12

Figure 1.3: describes symmetries Figure 1.5: Shows real atoms and bonds 2 X’s Note: Si and GaAs really do have spatially well defined covalent bonds. Not every crystal does Table 1.4  energy band diagrams Chp. 03 / ECE 931C VM Ayres, ECE874, F12

Cubic System Symmetries Standard unit cells Note: Most metals belong to fcc and bcc crystal systems. Metals do not have well defined covalent bonds. They have ‘fuzzy’ metallic bonds. VM Ayres, ECE874, F12

Problem 1.1: VM Ayres, ECE874, F12

Problem 1.1a: VM Ayres, ECE874, F12

Problem 1.1a: ½ atom top and bottom ¼ atom sides 2 x ½ = 1 4 x ¼ = 1 Equivalent of 2 atoms inside VM Ayres, ECE874, F12

Problem 1.1b: I used white boxes to cut off the outsides of the atoms, and then used group to create a few unit cells that I could move around and stack to create a crystal. VM Ayres, ECE874, F12

Problem 1.1b: Three parallel planes of atoms. Try moving them into position. Pattern is: 1 atom 4 atoms 1 atom 4 atoms 1 atom VM Ayres, ECE874, F12

Compare to standard unit cells: Problem 1.1c: I put the three parallel planes in place and then used more white boxes to hide everything else. Compare to standard unit cells: bcc VM Ayres, ECE874, F12

Problem 1.1c: Another choice for three parallel planes of atoms. But it would be harder to identify the bcc structure from this choice VM Ayres, ECE874, F12

Problem 1.1c: Another choice for three parallel planes of atoms. But it would be harder to identify the bcc structure from this choice VM Ayres, ECE874, F12