A New nBn IR Detection Concept Using HgCdTe Material

Abstract

This paper presents a new HgCdTe-based heterostructure to perform quantum infrared detection. The structure is based on the unipolar barrier concept, introduced by White in the 1980s for HgCdTe. The driving concept is the use of a large gap barrier layer to impede the flow of majority carriers (electrons on the conduction band in the case of n-type material) while facilitating the transport of minority (photo) carriers (holes on the valence band). The issue encountered here is the formation of a small potential barrier on the valence band, blocking photocarriers and therefore killing the quantum efficiency. The idea is to optimize the structure with an asymmetric barrier: abrupt on the contact side to efficiently block the majority carriers, and gradual on the absorption layer side to plane down the remaining potential barrier for the collected photocarriers. The concept has been studied by finite element modeling simulation and showed promising results. An optimal design has been identified in the middle wave band and molecular beam epitaxy layers have been grown then processed. First experimental characterization of the electrooptical properties of such structures showed promising features: 60% quantum efficiency and low turn-on voltage have been measured on single pixels.

Status of HgCdTe Barrier Infrared Detectors Grown by MOCVD in Military University of Technology

“…13 In HgCdTe material, proper p-type doping of the barrier reduces the valence band-offset and increases the offset in the conduction band. [14][15][16][17] The device with the barrier only in the conduction band is similar to that proposed in Ref. 1 in which a p-type barrier is interposed between two narrow gap n-type regions.…”

“…[14][15][16][17] This paper presents the status of MOCVD-grown HgCdTe barrier detectors, with emphasis on technological achievements in removing the valence band offset made recently at the Institute of Applied Physics, Military University of Technology (MUT).…”

Admittance of MIS Structures Based on nBn Systems of Epitaxial HgCdTe for Detection in the 3–5 μm Spectral Range

“…The development of nBn detectors based on HgCdTe grown by molecular beam epitaxy (MBE) is of interest because of the significant technological advantages over popular matrix photodiodes based on MBE HgCdTe, in which p-n junctions are usually created using a defect-forming ion implantation procedure [4]. Attempts at practical implementation of nBn detectors based on MBE HgCdTe are still few in number [5][6][7]. Recently, it was shown that it is possible to create medium-wavelength (3-5 μm, MWIR) MBE HgCdTe nBn detectors for which dark currents limited by hole diffusion were observed in the temperature range of 180-300 K [8].…”

Aдмиттанс МДП-структур на основе nBn-систем из эпитаксиального HgCdTe, разработанных для детектирования в спектральном диапазоне 3-5 μm

“…Создание nBn-детекторов на основе HgCdTe, выращенного методом молекулярнолучевой эпитаксии (МЛЭ), вызывает интерес из-за значительных технологических преимуществ перед популярными матричными фотодиодами на основе МЛЭ HgCdTe, в которых для формирования p−n-переходов обычно используется дефектообразующая процедура ионной имплантации [4]. Попытки практической реализации nBn-детекторов на основе МЛЭ HgCdTe пока немногочисленны [5][6][7]. Недавно показана возможность создания средневолновых (3−5 µm, MWIR) nBn-детекторов на основе МЛЭ HgCdTe, для которых в диапазоне температур 180−300 K наблюдались темновые токи, ограниченные диффузией дырок [8].…”