Inorganic Semiconductor Crystals

RMD is actively investigating several families of inorganic semiconductor crystals for gamma ray and neutron detection applications at room-temperature operation. The advantages of semiconductor detectors include good energy resolution for gamma ray spectroscopy and direct conversion of the input energy to an electrical signal. Material requirements for effective semiconductor devices include high atomic number for efficient gamma ray stopping, wide bandgap for low-noise room-temperature operation, and good carrier transport properties for effective charge collection. For neutron detection, RMD is developing novel compound semiconductors that contain boron or lithium as major constituents.

One of the most promising new classes of material for gamma ray detection is thallium bromide (TlBr) and its variants, TlBrI and TlBrCl. RMD is at the forefront of development of these materials through extensive purification and crystal growth techniques, as well as advanced device architecture and electrical contacts. TlBr offers an alternative to CdZnTe with higher gamma ray stopping power and potentially a lower-cost, higher-yield crystal growth process.

RMD was founded to pursue the development of cadmium telluride (CdTe) radiation detectors and we continue to develop this family of materials, including CdZnTe, CdMnTe, and other variants. Crystal growth of the CdTe-based materials is done using the Traveling Heater Method (THM), which was pioneered by RMD during the 1970s and continues to be a leading growth method for these materials.

Additionally, RMD continues to investigate a variety of other alternative compound semiconductor crystals for gamma ray and neutron detection. The critical need for novel neutron detectors has led RMD to develop semiconductors with boron or lithium constituents. Isotopes of lithium and boron have large cross-sections for neutron reactions that produce high-energy charged particles, which can be efficiently converted to electrical signals.
TlBr and TlBr0.35I0.65 Crystals

0.5-mm thick planar0.5-mm thick planar10-mm thick array10-mm thick20-mm thick array

TlBr Devices