Controlled growth of porous networks in phosphide semiconductors

Abstract

Pore networks in InP, as well as its ternary alloy with GaP, lattice matched to GaAs, are studied using scanning, transmission and high resolution electron microscopy techniques. The pores were grown by the electrochemical dissolution method along specific crystallographic directions. The applied etching current in galvanostatic and voltage in potentiostatic conditions are the key factors for the pore formation and direction, given a certain sample orientation and type of doping. Pores can be either crystallographically oriented (CO) in low current or current-like oriented (CLO) for increasing voltage and current densities. Scanning electron microscopy revealed that the CLO pores in InP tend to self-organized structures just below the nucleation layer, formed at about 50–80 nm from the free surface. Electron diffraction experiments showed that CO pores are readily formed along various crystallographic directions that depend linearly on the applied current value, resulting in a fully controllable pore formation mechanism. A three-dimensional pore network is thus feasibly accomplished in InP by periodically cutting off the dissolution process during the CLO pore formation or switching between CLO and CO pores, along with the organization of the CO pores on the basal (100) plane. High resolution observations showed that the single crystalline structure of InP is preserved in the vicinity of pores, illustrating the non-destructive nature of electrochemical dissolution. The formation of pores in Ga0.49In0.51P/GaAs heteroepitaxial layers takes place almost along the two [1\( \bar 1 \)1] and [\( \bar 1 \)11] directions.