Gate-dependent carrier diffusion length in lead selenide quantum dot field-effect transistors.

We report a scanning photocurrent microscopy (SPCM) study of colloidal lead selenide (PbSe) quantum dot (QD) thin film field-effect transistors (FETs). PbSe QDs are chemically treated with sodium sulfide (Na2S) and coated with amorphous alumina (a-Al2O3) by atomic layer deposition (ALD) to obtain high mobility, air-stable FETs with a strongly gate-dependent conductivity. SPCM reveals a long photocurrent decay length of 1.