Electron emission from silicon tip arrays controlled by np junction minority carrier injection

Abstract

The authors demonstrate for the first time the injection of electrons across an n-type to p-type silicon junction and their subsequent tunneling from approximately 1 μm tall p-type silicon points into a vacuum gap. The diffusive flow of these minority carriers in the p-type material is controlled by the application of a bias voltage in the form of a base contact metallization contact on the p-type silicon, in analogy with a bipolar junction transistor. Using an array density of 4×106 tips/cm2, the authors measured a maximum average current of 1 nA per tip. Increasing the base contact bias voltage from 0 to ∼1 V changes the emission from a supply limited regime typically observed with p-type silicon emitters, bringing the emitted current back to a linear Fowler–Nordheim characteristic similar to that observed previously by photon generation of carriers in p-type silicon tips. The authors finally note that in our short tips, minority carrier flow should be a nondissipative largely adiabatic diffusive transport process which is followed by extraction into vacuum. A novel heat extraction mechanism for future cooling applications is thus anticipated.