Gain and Dark Current Studies on Planar Photodetectors Made on Annealed GaAs-on-Si

Abstract

Interdigital, planar photodetectors were fabricated from annealed GaAs/Si heterostructures grown by molecular beam epitaxy using alloyed AuGe/Ni and non-alloyed Cr/Au contacts. The dark current and optical gain of the Cr/Au devices is higher than that of the AuGe/Ni devices. Contact degradation due to annealing and a p-like background doping consistently explains our data. The gain-optical power relationship follows a power 1aw with an exponent close to -1. PACS numbers: 73.50. Pz, 73.40.Sx, 85.60.Gz The growth of GaAs on Si allows the integration of GaAs devices with the Si technology [1-2]. However, the 4.1% large lattice mismatch results in a high defect density in the epilayer which alters the physical properties of the epilayer and the devices made of it. In this work, we study the dark current and photoresponse properties of planar, interdigitated GaAs/Si photodetection grown by molecular beam epitaxy (MBE). We analyze the effects of contact type, and compare our devices to those fabricated on Cr-doped, semiinsulating (SI) GaAs [3].The Si substrate was (100) p+-type 4° miscut towards [011]. A nominally undoped 2 m layer was first grown by MBE using a twostep method. We applied an unusually high growth rate to enhance growth planarity, and consequently, an epilayer quality [2]: the 50 nm buffer layer was grown with a 5 m/h growth rate at

Observation of the Coulomb Blockade at 77 K in a Lattice-Mismatched GaAs/Si Heterojunction

“…[2]). Formation of antiphase domains in that polar-on-nonpolar system was suppressed by simple misorienting the Si (001)-oriented substrate slightly toward the [011] direction.…”

“…The samples were supplied with good ohmic contacts: AuGe/Ni/Au alloy to n-type GaAs, and evaporated Al to p-type Si. These samples have been prepared to be studied as photodetectors [2]. We examined the current flowing throughout the heterojunction under forward bias at temperatures down to 77 K. No current measurement was possible in the temperature range of liquid helium so as the current carriers in Si were then frozen out.…”