Research On InAsSb/GaSb Interband Transition Quantum Well Infrared Photodetector

With the development of infrared detection,it has been widely applied in civil manufacture and living,scientific research,especially in the fields of modern national defense.Combined with the progress of semiconductor industry,photodetectors,such as the representative HgCd Te material,play an indispensible role in the fields of infrared guidance,reconnaissance,remote sensing,etc,due to their fast response and high sensitivity.The core goal of developing photodetectors is to seek for faster light response with higher signal-noise-ratio.It means that we must restrain the dark current and continuously increase the quantum efficiency.One way to achieve them is decreasing the operating temperature of photodetectors.However,it needs to equip photodetectors with a cooling system,which remarkably restrains the range of application and service life.Therefore,it is always a research hotspot to find applicable material that can be used to manufacture infrared detectors operating at higher even room temperature.Recently,it was reported that the restrained photo-excited carriers in low-dimensional semiconductor material could be effectively extracted from a p-n junction,such as InGa As/Ga As quantum well,InAs/Ga As quantum dot,InGaN/GaN quantum well.The extraction efficiency is up to more than 90%.Although it needs further research to figure out the internal mechanism of the phenomenon,the highly effective extraction of the restrained photo-excited carriers provides thoughts for designing novel photodetectors.It is promising to manufacture infrared detectors with higher signal-noise-ratio and operating temperature and longer response wavelength.Based on the previous work,the InAsSb/GaSb material system was selected as the research object to study a novel detector,interband transition quantum well infrared photodetector.It will provide experimental and theoretical support for infrared detection at higher temperature within the wavelength 3⁵?m.Firstly,the molecular beam epitaxy growth of GaSb and InAsSb thin layer were sdutied.We found the apropriate temperature and time for oxide desorption on the surface of GaSb substrate.Then,Hall Effect measure confirmed the n-doped concentration throuth growing 2?m Te-doped GaSb on GaAs substrate.Besides,the best V/III ratio for growth of GaSb was 9.The optimal temperature for growth of InAsSb was 430?.The protection time of asenic flux had important effects on the growth of InAsSb/GaSb multiple quantum wells.The shorter the open time was,the better the crystal quality of InAsSb was.Finally,through adjusting the open time of asenic shutter,we got matched InAsSb/GaSb multiple quantum wells.The antimony composition in InAsSb is 0.084 and the sample had good surface morphology with the root mean square roughness of 1.59?within an area of 2?m×2?m.When growing the strained InAsSb/GaSb multiple quantum wells,the antimony flux was increased and the antimony composition in InAsSb was 0.3.Then,the energy band of InAsSb/GaSb quantum well was calculated within the framework of effective mass approximation.The strong quantum confinement in such a structure results in an obvious increase of E₁ position compared with the conduction band of InAsSb.The interband transition energy of 5-nm thick InAs_0.91Sb_0.09embedded in the GaSb barrier was 0.53 eV?2.35?m?,which is accordance with the following experiment results.The fabricated photodetector exhibits a peak around 2.1?m at 300 K.The peak responsivity is 0.4 A/W under-0.5 V applied bias voltage,corresponding to a peak quantum efficiency of 23.8%in the case without any anti-reflection coating.At 300 K,the photodetector exhibits a dark current density of6.05×10^-3 A/cm² under-0.4 V applied bias voltage and 3.25×10^-5 A/cm² under zero,respectively.The peak detectivity is 6.91×10¹⁰ cm Hz^1/2/W at 300 K.Comparing the energy band calculation with experiment results,we can draw an important conclusion that the E₁ position must higher than the vale nce band of barrier material if one wants to measure the interband transition from valence band of InAsSb to E₁.Afterwards,several methods were explored to expand the response wavelength of the material system.O ne of them is increasing the Sb composition in InAsSb quantum well and keeping the same width of InAsSb.Because of the difficulty of material growth resulting from the increase of Sb composition,the method only increases the response wavelength to 2.55?m at 200 K heretofore.Another method is to broaden InAsSb to lower the E₁ position.However,the energy band calculation showed that the E₁ position would be lower than the valence band of GaSb when the width of InAsSb was 10 nm or more.Thus,the interband transition couldn't be detected.Finally yet importantly,we chose AlSb to replace GaSb as the barrier material,and the response wavelength of the fabricated prototype device was successfully increased to 3.03?m at 78 K.Those results will have important effects on finding appropriate material system and growth conditions.