Stable Native Oxides Formed on High Purity Germanium by Chemical Oxidation-A Novel Strategy for Surface Passivation

Phosphoric acid/hydrogen peroxide (H3PO4/H2O2) oxidizer mixture is used to grow films on high purity germanium (HPGe) crystals in Hydrofluoric acid with an objective to passivate the inter-contact region of HPGe detectors. The bonding characteristics have been investigated by IR transmission. The native oxide films consist of Ge-O bonding in cristalobite atomic configuration where both hexagonal and tetragonal germanium oxide signatures are present. Raman spectroscopy data indicate the amorphous nature of grown films. Scanning electron microscopy (SEM) clearly reveals formation of a porous layer that is Ge-H-x terminated as indicated by FTIR spectroscopy when high peroxide concentrations are employed for growth. On the other hand smooth and dense films appear at low H2O2 concentration with no Ge-H bonding signature. The chemically grown films are quite stable in HF unlike the unstable nature of native oxides of Ge. HPGe diode has been fabricated using lithium diffused and Pd surface barrier contacts. The inter-contact region is passivated using chemically grown oxide film. The film offers high resistive properties and inhibit surface leakage problem of the fabricated diodes.