P. Kurpas^a, M. Arens^b, D. Gutsche^a, E. Richter^a, M. Weyers^a

Published in:

J. Cryst. Growth, vol. 195, no. 1-4, pp. 217-222 (1998).

Abstract:

Reflectance anisotropy spectroscopy (RAS) was applied as in situ probe during the growth of GaInP/GaAs heterojunction bipolar transistors (HBT) under production conditions, i.e. wafer rotation. The amplitude of the oscillating signal (RAS transients taken at a fixed photon energy) gives the same information on surface anisotropy as obtained on static wafers. In these transients each layer of the HBT structure is represented by a specific signal amplitude. P-GaAs (3×10¹⁹ cm⁻³) and n-GaAs layers with different doping levels (10¹⁶–10¹⁸ cm⁻³) are distinguished. GaInP etch-stop and emitter layers cause pronounced interference structures that allow for the assessment of the emitter thickness on the nanometer scale. Due to its self-normalizing signal, RAS measurements are reproducible and largely not disturbed by wafer wobble, making this technique compatible with production requirements.

Keywords:

MOVPE; RAS; In situ monitoring; HBT; GaInP; GaAs; Doping

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