InP Materials
Abstract
The current objectives of this program are to improve the yield of high-purity polycrystalline InP as source material for crystal growth and to optimize the liquid-encapsulated Czochralski (LEC) method in order to grow crystals with low dislocation density and uniform dopant concentration. We have synthesized 35 ingots of InP with carrier mobilities at 77 K as high as 6800 sq cm/v/s. Using this charge material we have grown 26 nominally undoped LEC boules with mobilities at 77 K up to 42000 sq cm/v/sec and an additional 70 boules doped with Sn, Fe, S, Cd, Zn, or Cr. We have grown LEC crystals that are nearly dislocation-free up to a diameter of approx. 20 mm, without Zn or S doping, by increasing the thickness of the B2O3 encapsulant layer in order to reduce the radial temperature gradients in the growing boule. Although this procedure also reduces the vertical temperature gradient at the seed-melt interface, we were able to obtain reproducible twin-free growth in the lower gradient by modifying the pulling rod and its rotation mechanism to reduce system vibration. By means of x-ray topography and CO2 laser transmission studies we found that doped LEC crystals contain prominant growth striations, probably produced by random convection currents in the melt, that are associated with abrupt changes in dopant concentration. Measurements of infrared transmission at 10.6 microns were made on p-type InP samples to determine the free-carrier absorption due to holes. The absorption cross section is found to be much higher for holes than for electrons.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 1981
- Accession Number
- ADA110508
Entities
People
- Gerald W. Iseler
Organizations
- Massachusetts Institute of Technology