Mg doping of InGaN layers grown by PA-MBE for the fabrication of Schottky barrier photodiodes

This work reports on the fabrication of Schottky barrier based Mg-doped (In,Ga)N layers for fluorescence applications. Mg acceptors are used in order to compensate surface and bulk donors that prevent the fabrication of Schottky contacts on unintentionally doped (In,Ga)N layers grown by plasma-assisted molecular beam epitaxy (PA-MBE). Rectifying properties of the contacts exhibited a major improvement when (In,Ga)N : Mg was used. The electrical and optical measurements of the layers showed a hole concentration of up to 3 × 1019 holes cm−3 with a Mg acceptor activation energy of ~60 meV. Back-illuminated photodiodes fabricated on 800 nm thick Mg-doped In0.18Ga0.82N layers exhibited a band pass photo-response with a rejection ratio >102 between 420 and 470 nm and peak responsivities of 87 mA W−1 at ~470 nm. The suitability of these photodiodes for fluorescence measurements was demonstrated.