Optoelectronic UV LED and Neutron Detection Using Hexagonal Boron Nitride

Technology #d-0812

Hexagonal Boron Nitride Synthesized for Use in UV LED Optoelectronics and Neutron Detection

Optoelectronic devices, such as deep UV LEDs (deep ultraviolet light-emitting diodes) and neutron detection handheld devices can both be made using hexagonal boron nitride (hBN) semiconductor crystals. It has been difficult, in the past, to produce layers of hexagonal boron nitride crystals with the properties needed to enable wide use in optoelectronic devices and neutron detectors.  In this technology, hexagonal boron nitride has been synthesized in an improved crystalline form that will meet a variety of applications.

One major improvement is in the size of the crystalline layer produced. Thin layers of hexagonal boron nitride have been grown at up to 2 inches in diameter, which are considered “wafer scale”, meaning large enough to produce single wafers of crystal that are big enough to reduce production costs. Another improvement comes from “doping” the crystal by adding small amounts of magnesium (Mg) as the crystal grows. The addition of magnesium to the hexagonal boron nitride allows researchers to control and improve the material conductivity, which also improves its semiconducting properties. 

Hexagonal Boron Nitride Makes UV LED Optoelectronics More Energy Efficient, Smaller, and Better for the Planet

The use of hexagonal boron nitride in deep UV LED optoelectronic devices will have many advantages over existing and emerging technologies. Switching to hexagonal boron nitride semiconductors in UV LED optoelectronic devices will reduce the dependence on mercury-vapor lamps, which are currently the best options for generating UV light. Mercury vapor lamps contain toxic levels of mercury and must be disposed of as a hazardous material. UV LEDs have up to 70% lower energy consumption compared to mercury-vapor lamps. UV LEDs are also smaller in size and more durable and resistant to vibration and impact damage. In addition, the option of wafer-scale production of hexagonal boron nitride crystals will eliminate some steps in the chip-making process, rereducing production costs.

Previous researchers have developed aluminum gallium nitride (AlGaN) semiconductors for use as UV LEDs, but some of the material properties limit their efficiency to below 4%. Hexagonal boron nitride semiconductors are ten times more efficient than AlGaN semiconductors and the conductivity of the hexagonal boron nitride p-layer (which controls conductivity) is 6 to 7 orders of magnitude higher. Wafer-scale production of hexagonal boron nitride (a Group III nitride) also opens the door for further research opportunities in the area of Group III-nitride deep ultraviolet optoelectronics.

Boron Nitride Neutron Detectors Cost Less, Improve National Security

Hexagonal boron nitride neutron detectors will be simpler devices than the currently used Helium-3 neutron detection devices. This is because the neutron capture, charge collection, and electrical signal generation will all occur within a single chip of hexagonal boron nitride. Existing neutron detection technology relies on pressurized tubes containing Helium-3 gas. Helium-3 gas is rare and expensive, the glass tubes are fragile, and the devices are bulky and require high voltages to operate.  For these reasons, alternative neutron detection devices are being explored by many researchers.

Lowering the cost and improving the functionality and usability of neutron detection devices would increase the number of neutron detectors in use, increasing national security. Hexagonal boron nitride based neutron detectors don’t need Helium-3, they require low voltage, are compact and will be easily developed into handheld devices and chip-scale devices. Moving to hexagonal boron nitride-based neutron detectors will also eliminate issues with signal loss seen in current detectors. It is expected that, with improvements in hexagonal boron nitride synthesis, the efficiency of hBN semiconductor detectors will approach 100%.

Researches conducted tests on hexagonal boron nitride thin films to investigate their neutron detection efficiency. It was found that continuous irradiation with a thermal neutron beam generated a current response corresponding to a detection efficiency of nearly 80%. This is higher than the efficiency of Helium-3 detectors, which work at 70% efficiency.

Optoelectronic Hexagonal Boron Nitride Improve and Expand the Uses of UV LED and Neutron Detectors

Hexagonal boron nitride optoelectronic semiconductors can be used in UV LEDs, neutron detection devices, and in graphene electronics. The deep ultraviolet light that UV LEDs create is used to kill bacteria and sanitize drinking water, surface areas, and air in a variety of industries. It is also used in protein detection; in drug discovery; and in photocatalysis, such as in photo-activated air purifiers, where light is required for the reaction to occur. UV LEDs can also generate shorter wavelengths of UV light that are used to cure dental polymers; in the verification of UV barcodes; for fingerprint detection; for detection and analysis of bodily fluids in forensics; and in counterfeit money detec­tion.   

Neutron detectors made with hexagonal boron nitride will be used for radiation monitoring and detection in the nuclear power industry and in the medical industry. Neutron detectors are also used in nuclear fissile materials sensing which scans for illegal nuclear materials in shipments at port entries and at airports. Neutron detectors are also used by the military in nuclear treaty monitoring and in threat reduction activities.

Applications:

  • UV optical sensors and instrumentation
  • UV Identification verification
  • UV barcodes
  • Sterilization of surface areas and water
  • Forensic and bodily fluid detection and analysis
  • Protein analysis
  • Drug discovery
  • Medical light therapy
  • Polymer curing
  • Counterfeit money detection
  • Handheld neutron detection devices
  • Radiation monitoring and detection in the nuclear power industry
  • Radiation monitoring in the medical industry.
  • For nuclear fissile materials sensing
  • In nuclear treaty monitoring and threat reduction

Advantages:

  • UV LEDs will reduce dependence on mercury-vapor lamps
  • Will not contain mercury, which is a difficult to dispose of toxic material
  • Up to 70% lower energy consumption compared to mercury-vapor lamps
  • Smaller in size than mercury vapor lamps
  • More durable and resistant to vibration and impact damage.
  • Ten times more efficient than AlGaN semiconductors
  • Conductivity of the hexagonal boron nitride p-layer is 6 to 7 orders of magnitude higher. Wafer-scale production of hexagonal boron nitride increases research opportunities
  • Hexagonal boron nitride neutron detectors will be simpler than Helium-3 devices.
  • Neutron capture, charge collection, and electrical signal generation occur within the hexagonal boron nitride.
  • He-3 gas is rare and expensive and the glass tubes are fragile
  • He-3, devices are bulky and require high voltages to operate.  
  • Lowering the cost and improving the functionality and usability of neutron detection devices would increase the number of neutron detectors in use