Novel Terahertz Photoelectric Detection Mechanism And Detector Study

Terahertz?THz?is one part of the electromagnetic spectrum between microwave and infrared region.Due to its numerous unique properties,THz wave has shown great potential in security and medical imaging,examination of hazardous and poisonous articles,biomedical studies,next generation communication technology and astronomy researches.THz detection is an important component of THz science and technology and the foundation of multiple THz applications.Various THz detection methods have drawn worldwide attention in the recent years,while it still remains a major task to develop novel THz detectors with room-temperature operation ability,high sensitivity,fast response speed and structural simplicity which makes them easy to be integrated into line or focal plane arrays.In the hope of improving the abovementioned disadvantages,in this dissertation,we described a novel photoconductivity theory for highly sensitive THz detection under room temperature.Based on this theory,detector model was deduced,and novel THz detectors were fabricated utilizing narrow-band semiconductor In_0.53Ga_0.47As and InSb.Response of the detectors was characterized by the measurement system,and the application of this detector in room-temperature THz scan-imaging was explored.The main contexts and innovation points of this dissertation are as followed:1.A novel photoconductivity mechanism previously proposed by the group was described.The theoretical responsivity of the photodetectors designed and fabricated based on this mechanism was deduced in detail.The nature of this mechanism is to accomplish the detection of electromagnetic waves with photon energy far below band gap of semiconductors,while making use of the undulatory property of the electromagnetic wave.This is a breakthrough for the use of classic photodetectors applied in THz waveband.2.Based on the proposed novel photoconductivity mechanism,novel THz detectors was designed and fabricated utilizing ternary narrow-band semiconductor In_0.53Ga_0.47As thin film?IGA?and narrow-band semiconductor InSb;furthermore,the detector design was optimized and fabricated with an integrated log-spiral antenna.3.A measurement system was setup to characterize the detectors'response to sub-THz and THz radiation under room temperature.The results indicated that the IGA detector has achieve highly sensitive and fast response,with a noise equivalent power?NEP?lower than 10^-11 W/Hz^0.5 and time constant around 10^-510^-6 s;the InSb detector has achieve highly sensitive and fast response with NEP as low as 10^-13 W/Hz^0.5 and time constant around 10^-5s.4.We also assembled a temperature variable measurement system to record the response variation of the In_0.53Ga_0.47As THz detector to a sub-THz source in the temperature interval of 233²93 K.The response variation of the InSb THz detector to a sub-THz source and THz sources in the temperature interval of 77²97 K was recorded as well.By comparing the recorded response variations with theoretical predictions,as well as the measured responsivity with theoretically calculated ones,the proposed photoconductivity theory was confirmed and further developed.5.A THz scan-imaging system was assembled with the In_0.53Ga_0.47As THz detector operating as the receiving end.Using this system,images of an organic item and a metal item were successfully obtained,indicating the great potential of the designed detector in THz imaging.