Boron germanium—oxygen bonds

It is believed that most of the transition metals are complexed to nitrogen donors, such as are found in amino acids or derivatives of chlorophyll, and that the metals with high ionic potentials, such as beryllium, boron, germanium, titanium, gallium, and major elements such as aluminum and silicon, may be bonded to oxygen donors of degraded lignin. 

Similar arguments apply to impurity states. Any impurity which is bonded with its optimum valency is expected to form a part of the ideal network and contribute only to the conduction and valence bands. Oxygen, nitrogen, carbon, and germanium all behave in this way, forming alloys with a-Si H. Most of the phosphorus and boron atoms which are added as dopants, are in three-fold coordinated inactive sites... 

Framework silicates, also referred to as tectosilicates, are characterized by a tetrahedral ion-to-oxygen ratio of 1 2. The typical tetrahedral ions are silicon and aluminum, but, in some cases, germanium, titanium, boron, gallium, beryllium, magnesium, and zinc may substitute in these tetrahedral sites. All tetrahedral ions are typically bonded through oxygen to another tetrahedral ion. Silicon normally composes from 50% to 100% of the tetrahedral ions. 

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