Selective regrowth of Al0.30Ga0.70N p-i-n photodiodes

We report on the device performance of selective-area regrown Al0.30Ga0.70N p-i-n photodiodes. Tensile strain, induced by the lattice mismatch between AlxGa1-xN and GaN, leads to cracking above the critical thickness in layer s with high aluminum concentration. Selective-area regrown devices with les s than or equal to 70 mum diameters were fabricated without signs of cracki ng. These devices show low dark current densities with flat photoresponse a nd a forward turn-on current of similar to 25 A/cm(2) at 7 V. A quantum eff iciency greater than 20% was achieved at zero bias with a peak wavelength o f lambda =315 nm. A differential resistance of R-0=3.46x10(14) Omega and a detectivity of D*=4.85x10(13) cm Hz(1/2) W-1 was demonstrated. (C) 2000 Ame rican Institute of Physics. [S0003-6951(00)04844-0].