In this paper, we report AlGaAsSb/InGaAsSb heterojunction p-i-n photodetectors lattice-matched to GaSb substrates grown by solid source molecular beam epitaxy using As and Sb valved crackers. The use of valved crackers greatly facilitated the lattice-matching of the quaternary InGaAsSb absorbing layer to the GaSb substrates, as characterized by X-ray diffraction. The growth temperature of the absorbing layer in the device was kept at 450 degrees C. The V to III flux ratio was optimized based on comparison studies of the strength of photoluminescence (PL), which indicated excellent material quality of the InGaAsSb active layer lattice-matched to the GaSb substrates. The device structure was designed to be optimized for the maximum quantum efficiency. The p-i-n photodetectors were processed using wet chemical etching and standard photolithographic process. The resulting devices exhibited low dark current and a breakdown voltage of 32V at room temperature. A record Johnson-noise-limited detectivity, of 9.0 x 10(10)cm Hz(1/2)/W was achieved at 290 K. The 50% cutoff wavelength of the device was 2.57 mu m. Thus, our result has clearly demonstrated the potential of very high-performance lattice-matched InGaAsSb p-i-n photodetectors for the mid-infrared wavelengths, comparable or superior to the current InGaAs photodiodes on InP substrate with extended wavelengths. (C) 2008 Elsevier B.V. All rights reserved.