Speaker
Description
MARTHA (Monolithic Array of Reach-Through Avalanche Diodes) is a novel LGAD concept developed for future high-granularity timing detectors requiring simultaneous precision timing and high spatial resolution, as envisioned for next-generation collider experiments such as FCC-ee.
By introducing an additional low-doped n-layer between the n+ contact and the gain layer, the electric field distribution is sufficiently reduced to allow sensor pixelation without segmentation of the gain layer itself. As a consequence, MARTHA provides a true 100% fill-factor architecture while preserving intrinsic gain properties.
The MARTHA concept is currently in the proof-of-principle phase. So far, eight wafers featuring three different gain-layer implementations have been designed and produced by the Halbleiterlabor der Max-Planck-Gesellschaft (HLL-MPG) on 450 μm thick substrates. The initial substrate
thickness was chosen to address requirements from photon-science applications; future productions will optimize the implant design to be produced on thinner wafers, to achieve timing performance competitive with high-energy physics applications.
First characterization studies have been performed using Transient Current Technique (TCT) measurements and particle-beam tests. The voltage dependence of the gain and spread across the wafer of the three MARTHA variants was investigated using a 1060 nm infrared laser system.
Stable gains in the range 20-80 are obtained, which are larger than for typical LGAD (G∼10-20).
In addition, the timing performance of dedicated diode structures was studied during a beam campaign at the DESY II test beam facility. A timing resolution of 281 ps, after jitter subtraction, was obtained, in agreement with expectations for LGAD sensors of this thickness. Furthermore, strip sensors with a pitch of 100 μm were investigated using a dedicated readout system at the DESY II test beam facility with 5 GeV electron beams, to determine the MIP detection efficiency in the inter-strip region. These measurements provide a first validation of the MARTHA concept for highly segmented detector geometries.
This contribution presents the MARTHA sensor concept together with the first experimental characterization results from laboratory and test-beam measurements.