A few years ago, visible detection was demonstrated using advanced substrate thinning processes on flip-chip hybridized HgCdTe focal-plane arrays, in both French and US laboratories. Constant quantum efficiency was demonstrated at LETI-Sofradir from the short-wave infrared (IR) (2.5 μm cut-off) down to the visible range in 2006, validating complete CdZnTe substrate removal. This paper presents and discusses HgCdTe photodiode spectral response characterization, focusing on the short-wavelength part of the spectrum. We confirm the extended sensitivity of middle- and long-wave diodes: constant quantum efficiency has been observed from 10 μm down to 230 nm in the ultraviolet (UV). Such a unique property may be useful for very large-bandwidth spectrometers requiring monolithic detectors. Avalanche gain of middle-wave avalanche photodiodes has also been investigated in both the visible and the UV range. We demonstrate here that the avalanche gain remains constant while keeping a very low excess noise factor. This result opens the way to low-flux applications in this wavelength range.