Patent ID: 7755685

Claim:
A pixel for an imager, comprising: at least one electron multiplication (EM) gain stage configured in a loop and electrically coupled to a charge collection region and a charge readout region, said charge collection region being configured to generate a charge packet, said EM gain stage being configured to amplify the charge packet by impact ionization and to circulate the charge packet a predetermined number of times in one direction around said loop, said charge readout region being configured to receive the amplified charge packet and convert the amplified charge to a measurable signal, wherein said at least one EM gain stage comprises: a first clocked gate, a second clocked gate, a DC gate formed between said first clocked gate and said second clocked gate, and a second DC gate formed proximal to said first clocked gate and distal to said second clocked gate, wherein said first DC gate and said second DC gate are combined with a step potential profile under said first clocked gate and said second clocked gate so as to set a direction of flow of the charge packet around said loop.