Tellurium-induced defects in LPE Al0.36Ga0.64As

Abstract

The effect of Te doping on the growth of Al_0.36Ga_0.64As films has been studied. Variables investigated were Te concentration, growth rate, growth temperature, and heat treatment of the resultant films. Structural defects occur in Te‐doped films grown from 772 °C with a free‐carrier concentration as low as n=4×10¹⁷/cm³. A free‐carrier plateau is reached at n?2×10¹⁸/cm³. Surprisingly, electrically active Te is incorporated in Al_0.36Ga_0.64As at three distinct distribution coefficients. Focusing on the same variables in the temperature regime from 772 to 836 °C, transmission electron microscopy shows that high Te doping causes very high concentrations (10⁹/cm²) of small dislocation loops. These loops occur both over a wide range of growth solution doping at growth rates of 12 and 120 Å/sec. After heat treatment of these films at 820, 860, and 920 °C, substantially larger loops are observed. These loops are found to be extrinsic. In addition, the larger of these loops have small particles attached to them. The nature of the attached particles could not be determined. During heat treatment at 930 °C, dislocation loops could not be nucleated. Since Al₂Te₃ melts at 895 °C, it is assumed that below 895 °C Al₂Te₃ is the principal nucleating agent for the observed loops.