Selective epitaxial germanium on silicon-on-insulator high speed photodetectors using low-temperature ultrathin Si0.8Ge0.2 buffer

Abstract

The authors report the performance of selective epitaxial Ge ͑400 nm͒ on Si-on-insulator p-in mesa-type normal incidence photodiodes using ϳ14 nm low-temperature Si 0.8 Ge 0.2 buffer without cyclic annealing. At −1 V, very low bulk dark current densities of 1.5-2 mA/ cm 2 were obtained indicating good material quality, and the peripheral surface leakage current densities were 14-19.5 A / cm. For 28 m diameter round photodiode, the highest achieved external quantum efficiencies at −5 V were 27%, 9%, and 2.9% for 850 nm, 1.3 m, and 1.56 m optical wavelengths, respectively. 15ϫ 15 m 2 square photodiode has 3 dB bandwidth ജ15 GHz at −1 V. Good performance was achieved without high-temperature annealing, suggesting easy integration of Ge/ Si photodiode unto existing complementary metal-oxide-semiconductor process.

High-Efficiency p-i-n Photodetectors on Selective-Area-Grown Ge for Monolithic Integration

“…This very low bulk current density of 3.2 mA/cm 2 confirms the excellent Ge crystal quality and the shallow and abrupt n + junction in Ge with a high level of activation of n-type dopant, using in situ phosphorus doping during the epitaxial growth [13], [14]. This is one of lowest reported dark current density values among the Ge p-i-n photodiodes [2], [3], [15]- [17]. Fig.…”

Dark current analysis in high-speed germanium p-i-n waveguide photodetectors

“…It increases to a mean value of 92 nA and 542 nA as the Ge layer is scaled to 29.4 m wide. It can be seen that there are some outlier dark current data points for the 29.4 m wide Ge device, which is attributed to the inferior material quality in the large area Ge devices [15][16][17]. These outlier data points were removed from the dark current modeling.…”

Strong Electro-Absorption in GeSi Epitaxy on Silicon-on-Insulator (SOI)

“…All measured diodes exhibited strong rectifying characteristics with low dark current densities. In particular, the dark current densities for 100 µm radius diodes at nominal bias of −1 V are ~5 mA/cm 2 (0.05 nA/µm 2 ), which are at least 2-3 times lower than Ge diodes grown with standard two-step growth [33][34][35]. The main root cause of leakage current in junction devices is the dislocations in the intrinsic region, which act as the generation and recombination centers for carriers.…”