Comparison of multiquantum well, graded barrier, and doped quantum well GaInAs/AlInAs avalanche photodiodes: A theoretical approach

A comparison of the multiquantum well; graded barrier, and doped quantum well Ga0.47In0.53As/Al0.48In0.52As avalanche photodiodes (APD´s) is presented based on the calculated gain, excess noise factor, bandwidth, and gain-bandwidth product. A general numerical method, based on an ensemble Monte Carlo calculation, is used to determine the device performance, measured in terms of the electron and hole ionization probabilities, as a function of the device geometries and applied electric field. From a determination of the ionization rates, critical performance figures such as the gain, excess noise factor, and bandwidth can be determined. Various device geometries are examined (different layer widths, dopings, and overall applied electric field strength) among the three device types. The results indicate that the doped quantum well device gives the largest gain-bandwidth product at the lowest noise factor of the three device types. Surprisingly, the highest absolute gain is achievable in a simple multiquantum well APD, but at a much smaller bandwidth than in a doped quantum well device. At comparable device sizes, the doped quantum well device can deliver roughly two orders of magnitude more gain and gain-bandwidth product than either the simple multiquantum well or graded barrier device.