A type II superlattice detector uses alternating thin layers of two different semiconductors, typically from the InAs/GaSb material system, arranged so that the conduction and valence bands overlap in a way that lets the effective bandgap be tuned by layer thickness. A quantum well infrared photodetector instead relies on intersubband transitions within a single well material, usually GaAs-based, to absorb infrared light. Both are used to reach cutoff wavelengths not easily achieved with bulk narrow-gap semiconductors like HgCdTe. In this dataset the two families are searched together because patent claims frequently address shared problems such as dark current suppression and cutoff wavelength tuning across both structures.

The dataset shows filings peaking at 47 in 2017 and falling in the tracked window that follows, with the 2021-to-2024 span down 67% from 21 to 7. This does not necessarily mean the underlying research has slowed; it may reflect consolidation of filing activity into fewer, more targeted applications, or a shift toward trade secret protection for process know-how like molecular beam epitaxy recipes. Publication lags filing by roughly 18 months, so the 2025 and 2026 figures in any such dataset are structurally incomplete and should not be read as continuing evidence of decline.

The ranking in this dataset covers 100 companies and research organisations, with the leading assignee holding 91 of the 879 records in scope — well ahead of the fifth-place holder at 36. The top five combined account for 35.4% of all records, and the top ten reach 48.8%, meaning close to half of the field’s activity sits outside these ranked leaders in a long tail of smaller filers. The group includes a mix of research institutions, government-linked defence entities and industrial semiconductor manufacturers, rather than being dominated by a single sector.