The embodiments of the disclosure relate generally to photovoltaic devices with broad band absorption in the solar light spectrum incident to Earth. The devices include integrated layers of graphite oxide and reduced graphite oxide, which exhibit intrinsic p/n junctions, which can be self-biasing and allow for production and separation of electron-hole pairs that can drive the current in the device. Descriptions of the devices and methods of making the structures are disclosed.

A method for manufacturing a semiconductor apparatus includes a step of preparing a first semiconductor substrate, a second semiconductor substrate including a first semiconductor layer and a second semiconductor layer, and a third semiconductor substrate, a bonding step of bonding the second semiconductor substrate and the third semiconductor substrate to one main surface of the first semiconductor substrate, and a thinning step of removing at least the second semiconductor layer of the second semiconductor substrate by wet etching after the bonding step. The first semiconductor layer includes a P type impurity region or an N type impurity region, the second semiconductor layer includes a P+ region. An etching rate of an etchant used in the thinning step for the second semiconductor layer is higher than an etching rate for the first semiconductor layer.