  Low Gain Avalanche Diodes (LGADs) are thin (20-50 $\mu m$)silicon di ode
sensors with modest internal gain (typically 5 to 50) and exceptional time
resolution (17 $ps$ to 50 $ps$). However, the granularity of such devices is
limited to the millimeter scale due to the need to include protection
structures at the boundaries of the readout pads to avoid premature breakdown
due to large local electric fields. In this paper we present a new approach --
the Deep-Junction LGAD (DJ-LGAD) -- that decouples the high-field gain region
from the readout plane. This approach is expected to improve the achievable
LGAD granularity to the tens-of-micron scale while maintaining direct charge
collection on the segmented electrodes.
