Low noise p-channel JFETs for X-ray spectroscopy with silicon drift detectors

We present noise performance of different p-channel JFETs fabricated by silicon-detector compatible technology. This JFET can be used as a front-end transistor of a resistorless charge preamplifier for low energy X-ray detection. Our concern is the read-out of silicon drift detectors. Firstly, a fully implanted p-channel JFET was fabricated by an optimized DIMES-03 process (temperature budget of 950°C). The JFET is top-gate driven with W/L=100/1. We have measured the white series noise of 2.9 nV/√Hz and the corner frequency of the 1/f noise of ~500 Hz. This JFET is therefore a very good alternative for an external front-end transistor for low noise charge preamplifiers. To achieve further improvement, an integration of this JFET into the read-out anode of the drift detector is necessary. We present the modified DIMES-03 process which was used to fabricate p-JFETs on low- and high-ohmic wafers. The noise parameters measured on these JFETs will be discussed