Reactant vaporizer and related systems and methods

A solid source chemical vaporizer, comprising:

• a housing base;
• a first tray configured to be housed within the housing base, the first tray defining a first serpentine path adapted to hold solid source chemical and allow gas flow thereover, the first serpentine path comprising a plurality of antiparallel segments within a first plane;
• a second tray configured to be housed within the housing base vertically stacked above the first tray, the second tray defining a second serpentine path adapted to hold solid source chemical and allow gas flow thereover, the second serpentine path comprising a plurality of antiparallel segments within a second plane parallel to the first plane, wherein the first serpentine path and the second serpentine path are configured to be switchably arranged between series and parallel arrangements;
• and
• a housing lid.