EFFECTS OF GROWTH INTERRUPTION UPON SILICON DELTA-LAYER IN GALLIUM-ARSENIDE

We describe a study of samples grown by molecular-beam epitaxy, design ed to examine the limitations to silicon (Si) delta-doping of gallium arsenide (GaAs) at elevated growth temperatures. Samples (Si delta-dop ed to 1 x 10(13) cm(-2)) were grown at 630 degrees C, during which the growth was paused (for times between 0 and Is min) after depositing t he Si. Total electron sheet densities were measured (using Hall and Sh ubnikov-de Haas (SdH) effect measurements) to determine the electrical ly active Si concentration. The free electron concentration showed a r eduction from about 8 x 10(12) cm(-2) for zero pause time, to 5 x 10(1 2) cm(-2) for 18 min pause time. These results can be explained convin cingly using simple models of impurity background in the MBE chamber o r surface aggregation. Further experiments to distinguish these mechan isms are discussed. (C) 1998 Elsevier Science B.V.