Accession Number:

AD0609016

Title:

THEORY OF SEMICONDUCTOR-TO-METAL TRANSITIONS

Descriptive Note:

Technical rept.

Corporate Author:

HARVARD UNIV CAMBRIDGE MA DIV OF ENGINEERING AND APPLIED PHYSICS

Personal Author(s):

Report Date:

1964-08-26

Pagination or Media Count:

182.0

Abstract:

Several materials undergo transitions from a semiconducting to a metallic state at a critical temperature. Previous theoretical attempts to understand such transitions have been generally qualitative and have not been able to account for all the specific experimental results. In this work, an explanation of semiconductor-to-metal transitions is presented using a band model. It is shown thermodynamically that the energy gap of a semiconductor closes down significantly with the number of excited carriers if the gap has a large pressure coefficient, as is found in several of these materials. This shrinkage of the energy gap is due to explicit variation of the crystalline volume. There may also be a constant volume carrier concentration dependence of the gap, which cannot be evaluated thermodynamically. The experimental results dealing with the crystals which exhibit semiconductor-to-metal transitions are presented, and the predictions of the theory are tested. Very good agreement is obtained.

Subject Categories:

  • Inorganic Chemistry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE