Optically pumped vertical external-cavity surface-emitting lasers (OP-VECSELs) have shown impressive performance with high average output power in both continuous-wave (cw) and passively modelocked operation using semiconductor saturable absorber mirrors (SESAMs). Electrical pumping (EP) is a key factor for more compact and cost efficient modelocked VECSELs suitable for low-cost mass applications such as optical clock-rate distribution in microprocessors, chip-to-chip interconnects or optical telecommunication systems. This thesis describes the design, fabrication and performance improvement of an EP-VECSEL optimized for passive modelocking. An initial realization of an EP-VECSEL is presented, which demonstrated confined Gaussian-like current injection profiles and up to 120 mW of output power in cw multi-mode operation. A detailed investigation of the beam quality of EP-VECSELs is discussed and reveals important guidelines for achieving excellent beam quality with reasonable output power levels. Furthermore, an in-depth characterization of important gain properties is given and broadens the physical understanding of these devices. Moreover, an optimized EP-VECSEL is presented, which enabled up to 170 mW of output power in cw multi-mode operation and 26 mW in fundamental transversal mode operation. This was made possible by improving various design aspects of the devices. Passively modelocking the optimized EP-VECSELs with a SESAM led to 7.3-ps pulses with 13.1 mW of average output power at 1.46 GHz repetition rate. Furthermore, a record-low pulse duration of 6.3 ps was obtained, the shortest pulses from a passively modelocked EP-VECSEL so far.weiterlesen