CHINESE JOURNAL OF PHYSICS VOL. 39, NO. 4 AUGUST 2001

Transport and Optical Studies of the D^--Conduction Band in Doped
GaAs/AlGaAs Quantum Wells

C. H. Lee¹, Y. H. Chang¹, C. F. Huang¹, M. Y. Huang¹,
H. H. Lin², and C. P. Lee<sup>3

1</sup>Department of Physics, National Taiwan University, Taipei, Taiwan 106, R.O.C.
²Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan 106, R.O.C.
³Institute of Electronics, National Chiao-Tung University, Hsin-Chu, Taiwan 300, R.O.C.
(Received March 23, 2001)

The properties of D^- ions in quantum wells were studied. It is found that, with an intermediate concentration of D^- ions, electrons in the quantum wells possess both band-like and impurity-like properties. The appearance of the Quantum Hall effect makes it possible to rule out the existence of an impurity band that is separated from the conduction band. The results are interpreted in terms of the formation of a D^- conduction band, with the D^- band becoming a tail of the conduction band. The implications of our experimental results on the metal-insulator transitions in doped semiconductors are discussed.

PACS. 71.30.+h - Metal-insulator transitions and other electronic transitions.
PACS. 73.20.Jc - Delocalization processes.
PACS. 71.55.Eq - III-V semiconductors.

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