Abstract
The influence of post-growth annealing on the electrical properties, the transient carrier dynamics and the performance as THz photoconductive receiver of Beryllium (Be) doped InGaAs/InAlAs multilayer heterostructures grown at 130 °C in a molecular beam epitaxy (MBE) system was investigated. We studied samples with nominally Be doping concentrations of 8 ×10 17 cm-3 – 1.2 ×1019 cm3 annealed for 15 min. – 120 min. at temperatures between 500 °C – 600 °C. In contrast to previous publications, the results show consistently that annealing increases the electron lifetime of the material. In analogy to the annealing properties of low-temperature grown (LTG) GaAs we explain our findings by the precipitation of arsenic antisite defects. The knowledge of the influence of annealing on the material properties allowed for the fabrication of broadband THz photoconductive receivers with an electron lifetime below 300 fs and varying electrical properties. We found that the noise of the detected THz pulse trace in time-domain spectroscopy (TDS) was directly determined by the resistance of the photoconductive receiver and the peak-to-peak amplitude of the THz pulse correlated with the electron mobility.
Highlights
Within the last decades low-temperature growth of III-V compounds has become an important technique for the fabrication of semiconductors with sub-picosecond carrier lifetime and semiinsulating properties
The density of trapping sites is significantly higher than the density of excited carriers such that the differential transmission (DT)-signal decays mono-exponentially and the electron lifetime can be determined by mono-exponential fits to the data.[21,31]
We investigated the influence of annealing on the electrical properties, the carrier dynamics and the performance as THz photoconductive receiver of Be-doped low-temperature grown (LTG)-InGaAs/InAlAs multilayer
Summary
Within the last decades low-temperature growth of III-V compounds has become an important technique for the fabrication of semiconductors with sub-picosecond carrier lifetime and semiinsulating properties. The most prominent examples of low-temperature grown (LTG) semiconductors are GaAs and InGaAs.[1] Whereas the properties of LTG-GaAs have been studied extensively within the last 35 years, only a few studies of LTG-InGaAs exist. The principal applications are semiconductor saturable absorber mirrors (SESAMs),[2] which are applied for the passive mode-locking of femtosecond fiber-lasers, and photoconductors for the generation and detection of THz radiation.[3,4] LTG-InGaAs based photoconductors are the state-of-the art detector antennas in commercially available THz time-domain spectroscopy (THz-TDS) systems.[5,6] the improvement of devices fabricated from LTG-InGaAs based materials demands a fundamental understanding of the properties of the material itself. III–V of this publication we give a short summary of the state of knowledge about LTG-GaAs and LTG-InGaAs and point out similarities, differences and open questions
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