Low excess noise APD with detection capabilities above 2 microns

In this work, we present the study on Separate Absorption, Charge and Multiplication (SACM) APDs utilising In_0.52Al_0.48As as the multiplication layer and In_0.53Ga_0.47As/GaAs_0.51Sb_0.49 periodic heterostructures as the absorption layer. In_0.52Al_0.48As lattice matched to InP has been shown to have superior excess noise characteristics and multiplication with relatively low temperature dependence compared to InP. Furthermore, the type-II staggered band line-up of In_0.53Ga_0.47As/GaAs_0.51Sb_0.49 heterostructures leads to a narrower effective bandgap of approximately 0.49 eV corresponding to the APD cut off wavelength of 2.4 μm. The SACM APD exhibited low dark current densities near breakdown. The device also exhibited multiplication in excess of 100 at 200 K. The excess noise of the APD was low as expected, and is comparable to that of a 1 μm In_0.52Al_0.48As PIN diode.