Politecnico di Torino - Corso Duca degli Abruzzi, 24 - 10129 Torino, ITALY

+39 011 090 6100 info@tech-share.it

Rectifier for a THZ band radiation sensor

CMOSDetectorsImagingradiation sensorTerahertz

Introduction

New approach to THz detectors derived from the direct integration of the antenna with a rectifier device obtained by modifying the commercial CMOS (Complementary metal–oxide–semiconductor) active pixel image sensor. The antenna and the rectifier device form a “rectenna” structure which, when exposed to electromagnetic radiation, causes the injection of charge into the collection bag (SW). The charge can be collected during an integration time.

Technical features

The structure has the edge of the metal electrode in contact with the implanted p-type surface layer, forming a metal-semiconductor junction. The edge of the antenna thus becomes a part of the electronic device. The semiconductor of the SW completes the structure of the rectifier. The working function of the metal must be such as to guarantee a position of the Fermi level like that of highly doped silicon; for example, titanium (Ti) with a work function of 4.33 eV, a material compatible with CMOS technology, can be used as the terminal part of the electrode. With the working function Ti, the contact gives rise to a straightening junction with the “p + Si” layer. The p-Si layer under the electrode must have a controlled thickness that can be easily implemented by choosing the dose and energy of the ion implant. Due to its reduced thickness, the p-Si region becomes almost completely deflected by the caportatori, giving rise to a reduction of the barrier, to a value of 0.3-0.5 eV compared to the conduction band of the silicon inside SW.

Possible Applications

  • Monitoring systems for materials in production;
  • Sensing of chemical, biological processes;
  • Security and defence systems against explosives.

Advantages

  • High sensitivity and low cost;
  • It can be used to protect sensitive elements from interaction with the environment;
  • It can be used where the ability to control the interactions between multiple features is required.