Anomalous Diffusion of Tin in GaAs

Abstract

We have used a “leaky tube” diffusion system to carry out tin diffusion in p‐type normalGaAs substrates in an attempt to produce n‐p junctions with a low temperature processing technique. Solid normalSnS was used as the source for the tin, and the diffusions were carried out in the temperature range 650°–750°C for times varying from 2 to 24h. Both secondary ion mass spectrometry (SIMS) and Rutherford backscattering spectrometry (RBS) showed that tin had been introduced into the substrates in concentrations as high as 3.3E+19 cm−3 and to depths as large as 2 μm. However, electrochemical carrier concentration profiling revealed that the diffused region remained p‐type with net carrier concentration barely altered by the diffusion process. The reason for this anomalous behavior is not understood, but pairing or some other compensation may be taking place.

Light emission from silicon with tin-containing nanocrystals

“…The STEM data demonstrate that the variations in the nanocrystal size and number density are rather limited, taking the quite broad range of annealing temperatures into account. This is consistent with the fact that a Sn atom requires a vacancy to assist its diffusion 22 . These vacancies are most likely present from the initial lowtemperature MBE growth process 23 and available during both the first Sn-Sn segregations steps 24 and the following coarse precipitation stage, which must take place at a temperature below 650 • C. In other words, for the MBE- grown samples, the Sn precipitation does not depend on thermally generated vacancies, which explains the limited variations in the nanocrystal size distribution on annealing temperature.…”