  New generation Cadmium Telluride (CZT & CdTe) solid state detectors can
provide high quantum efficiency with reasonably good energy resolution and can
operate at near room temperature; an unique advantage for space experiments. We
present here results of our study of small diode detectors as well as large
area pixel detectors. Our study is aimed at developing near room temperature
hard X-ray spectroscopy detectors for ASTROSAT and other future Indian space
science missions.We have studied a Si-PIN detector in the energy range 5 - 60
keV and CZT & CdTe Schottky diode detectors in the energy region 10 - 1330 keV.
We have studied large area (64 cm$^2$) CZT pixel detectors with pixel size
close to the small CZT detector. We have studied individual pixels as well as
CZT detector as a whole (summed over all the 1024 pixels). The energy
resolution behaviour of the large area CZT detector is similar to that of small
diode detectors in the low energy region. The change in operating temperature
from room temperature ~20 to ~70$ degree C drastically affects both the energy
resolutionas well as the peak area due to a sharp rise in the thermal
noise.These results suggest that the cooling of detector system will provide
better energy resolution as well as detection efficiency.
