. "direct bandgap" . "direct band gap" . "indirect band gap" . "direct bandgap semiconductor" . . "direct" . . "indirect band-gap" . "direct band-gap" . "momentum change" . "indirect bandgap" . . "indirect gap" . . "Direct and indirect band gaps" . . "\\\"direct bandgap\\\"" . "Direct and indirect band gaps" . "ind." . "Indirect bandgap" . . . . "direct-gap" . "indirect" . "direct-gap semiconductors" . "direct allowed" . "direct or indirect" .