Abstract
We present a fast and robust optical method of determining carrier concentrations in heavily doped layered structures. We discuss several advantages of the technique as compared to other, more commonly applied methods using as an example InAs based devices used for THz radiation generation. Our approach leads to a more accurate estimation of doping levels in the investigated structures and aids the standard Hall measurements in precise predictions of radiative efficacy in the THz region. Predicted enhancement factors reproduce THz-Time Domain Spectroscopy (TDS) experiment results within a 2 % accuracy.
Highlights
The knowledge of doping levels in semiconductor structures may be considered paramount from the point of view of fabrication of many devices requiring either n- or p-type doped layers
It is an extremely significant factor in the case of terahertz emitters utilizing InAs doped layers (Kozub et al 2015) and in case of mid infrared semiconductor lasers (both Quantum Cascade Lasers (QCLs) Ohtani and Ohno 2003; Teissier et al 2004 as well as Interband Cascade Lasers (ICLs) Yang 1995), where doped InAs layers are used for a plasmon-based enhancement of waveguiding properties (Tian et al 2010)
In this work we focus on InAs based THz emitters utilizing the Photo–Dember effect for radiation generation (Kozub et al 2015)
Summary
The knowledge of doping levels in semiconductor structures may be considered paramount from the point of view of fabrication of many devices requiring either n- or p-type doped layers. In this work we focus on InAs based THz emitters utilizing the Photo–Dember effect for radiation generation (Kozub et al 2015) They can be classified among semiconductor surface generation methods which constitute one branch of THz sources beside the commonly used low temperature (LT) grown GaAs antennas and organic crystals (4-N,N-dimethylamino-40-N0-methyl stilbazolium tosylate (DAST) crystals being perhaps the most notable). One significant advantage of these generation methods is the ease of pump beam alignment when compared to LT-GaAs antennas and lower average pump beam power usualy present in organic crystals. This makes InAs emitters enticing for various THz applications, to efficiently characterize them one needs to know the level of carrier concentration within one of it’s layers
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