hw2 - distances have been kept the same What kind of...

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ECE 440 Homework II Spring 2006 Due: Monday, January 30, 2006 1. (a) A GaAs semiconductor crystal is doped with silicon atoms. If all silicon atoms displace Ga atoms, does the crystal become an n-type or p-type material? Why? What if 3/4 silicon atoms displace Ga atoms while 1/4 silicon atoms displace As atoms? Is the sample n-type or p-type? (b) In practice, when GaAs is doped with carbon atoms, it tends to become p-type. Do the carbon atoms preferentially displace Ga or As atoms? 2. Assume that a perfect GaAs has gone through a hypothetical processing so that all gallium and arsenic atoms are completely and randomly mixed and redistributed yet all inter-atomic
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Unformatted text preview: distances have been kept the same. What kind of crystal structure is this hypothetical GaAs now, a diamond or zinc blende? Would it become n-type or p-type if it is doped with selenium? 3. (a) Using Appendix III, which of the listed semiconductors in Table 1-1 has the largest band gap? The smallest? Is there a noticeable pattern in the band gap energy of III-V compounds related to the column III element? (b) Among the indirect materials listed in Appendix III, which one has the smallest bandgap energy, and what is that at room temperature? Which one has the largest bandgap energy, and what is that?...
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