Realising a solid state photomultiplier and infrared detectors through Bismide containing semiconductors

Lead Research Organisation: University of Surrey
Department Name: ATI Physics

Abstract

Semiconductors are commonly used in imaging sensors and solar cells, as they can directly convert light into an electrical current. The highest band of electron energies that are fully occupied is known as the valence band while the lowest unfilled energy band is the conduction band. The energy difference between the conduction and valence bands is known as the bandgap. When electrons from the valence band are excited into the conduction band by absorbing light with energy equals to or greater than the bandgap, the change of charges induces an electrical current. Consequently the bandgap is the most important parameter in the design of semiconductor photodetectors. While visible wavelength photodetectors are widely available, detectors for infrared wavelengths are significantly less mature and more costly. Progress in infrared detectors has been hindered by the limited choice of bandgaps currently available. In this work we will introduce a novel approach, by incorporating Bismuth (Bi) atoms into existing semiconductors such as InAs and InGaAs, to achieve a wide range of bandgap energies to detect infrared signals across a correspondingly wide wavelength range. Achieving this will lead to a new range of infrared detectors that can have transformative impact on applications including night vision imaging, medical diagnostic sensors, environmental monitors and for accurate temperature measurements in manufacturing processes.

We will also exploit Bi-alloys to engineer a noiseless charge amplification process in photodiodes known as avalanche photodiodes (APDs). When an electron leaves the valence band a vacant state (a hole) is created. Therefore an electron and a hole are created as a pair of charges in semiconductors. Properties of the conduction and valence bands will determine how electrons and holes gain energy from an applied electric field. In materials such as InAs, electrons gain energy at a much faster rate and travel at higher velocity too, when a voltage is applied. Therefore InAs is an excellent material for high speed electronic devices and also for providing internal signal amplification in APDs. When designed appropriately, the energetic electrons in InAs APD ensure that the amplification process, known as impact ionisation, is coherent so that negligible amplification noise is generated. In this work we will incorporate Bi into InAs to alter the valence band such that only electrons will gain significant energy from the electric field. This ability to suppress energetic holes will allow us to design very high gain APD across a wide range of electric field while concomitantly suppressing the noise associated with impact ionisation. By carefully controlling the fraction of Ga and Bi atoms, we will also develop a range of InGaAsBi APDs suitable for detecting a wide range of infrared wavelengths.

The proposed research to introduce a new class of Bi-containing infrared detectors and APDs, will be carried out by a carefully assembled team of world leading researchers from Universities of Sheffield and Surrey, in collaboration with the Tyndall National Institute, as well as partners from LAND Instruments, Laser Components and the UK Quantum Technology Hubs in Enhanced Quantum Imaging. Our work will start with a focus on formulating growth conditions (such as temperature and atomic fluxes) to obtain high quality InGaAsBi crystals. Following an intensive crystal growth programme, we will develop procedures to fabricate the grown InGaAsBi semiconductors into devices for a wide range of measurements to extract key material parameters. A model that accurately describes the bandstructure of InGaAsBi will be developed so that we can use them to design high performance infrared detectors and APDs. These newly engineered devices will be evaluated with our industrial partners for applications ranging from temperature measurements in manufacturing to novel imaging techniques using quantum properties of light.

Publications

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Description This project led to an improved understanding of the growth of new types of compound semiconductor containing bismuth. These semiconductors are of growing interest owing to their applications in higher efficiency lasers, photodetectors and photovoltaics.
Exploitation Route The outputs will be used to help develop improved quality semiconductor materials for use in photonic and electronic device applications.
Sectors Aerospace, Defence and Marine,Chemicals,Digital/Communication/Information Technologies (including Software),Energy

 
Title Quantifying Auger recombination coefficients in type-I mid-infrared InGaAsSb quantum well lasers 
Description From a systematic study of the threshold current density as a function of temperature and hydrostatic pressure, in conjunction with theoretical analysis of the gain and threshold carrier density, we have determined the wavelength dependence of the Auger recombination coefficients in InGaAsSb/GaSb quantum well lasers emitting in the 1.7-3.2 µm wavelength range. From hydrostatic pressure measurements, the non-radiative component of threshold currents for individual lasers was determined continuously as a function of wavelength. The results are analysed to determine the Auger coefficients quantitatively. This procedure involves calculating the threshold carrier density based on device properties, optical losses, and estimated Auger contribution to the total threshold current density. A strong increase with decreasing mid-infrared wavelength (< 2 µm) indicates the prominent role of intervalence Auger transitions to the split-off hole band. Above 2 µm, the increase with wavelength is approximately exponential due to CHCC or CHLH Auger recombination. The observed dependence is consistent with that derived by analysing literature values of lasing thresholds for type-I InGaAsSb quantum well diodes. Over the wavelength range considered, the Auger coefficient varies from a minimum of 1x10 -16cm 4s -1 at 2.1µm to ~8x10 -16cm 4s -1 at 3.2µm. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
URL https://zenodo.org/record/3907414
 
Title Quantifying Auger recombination coefficients in type-I mid-infrared InGaAsSb quantum well lasers 
Description From a systematic study of the threshold current density as a function of temperature and hydrostatic pressure, in conjunction with theoretical analysis of the gain and threshold carrier density, we have determined the wavelength dependence of the Auger recombination coefficients in InGaAsSb/GaSb quantum well lasers emitting in the 1.7-3.2 µm wavelength range. From hydrostatic pressure measurements, the non-radiative component of threshold currents for individual lasers was determined continuously as a function of wavelength. The results are analysed to determine the Auger coefficients quantitatively. This procedure involves calculating the threshold carrier density based on device properties, optical losses, and estimated Auger contribution to the total threshold current density. A strong increase with decreasing mid-infrared wavelength (< 2 µm) indicates the prominent role of intervalence Auger transitions to the split-off hole band. Above 2 µm, the increase with wavelength is approximately exponential due to CHCC or CHLH Auger recombination. The observed dependence is consistent with that derived by analysing literature values of lasing thresholds for type-I InGaAsSb quantum well diodes. Over the wavelength range considered, the Auger coefficient varies from a minimum of 1x10 -16cm 4s -1 at 2.1µm to ~8x10 -16cm 4s -1 at 3.2µm. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
URL https://zenodo.org/record/3907415
 
Title Light Emitting Semiconductor Device 
Description This patent concerns the use of bismuth containing alloys to produce high efficiency photonic devices. 
IP Reference US20120168816 
Protection Patent application published
Year Protection Granted
Licensed Commercial In Confidence
Impact This work has spawned a field of research and development in new materials for photonic devices. The applications include telecommunications and sensing.
 
Title Light Receiving Device 
Description This patent application concerns the use of novel III-V alloys for use in the development of high efficiency solar cells. 
IP Reference US20160149060 
Protection Patent application published
Year Protection Granted
Licensed No
Impact This IP has led to research into new approaches for solar cell design and helped to stimulate a new research topic on photodetectors.